ARE.  YOU.  SERIOUS!?
  Not to sound ungrateful, but let's break this down.
Eldritch Strike sounds nice on paper.  Hit a dude, they have Disadvantage on a Saving Throw from a spell YOU cast before the end of your next turn.  That's nice, I guess.  Snag Hold Person and you've got a clutch setup for you and your allies; in fact, because you can switch up the order (in most cases) of your Bonus Action and Action economy, you can achieve this debut in the same round.  ...Still only hitting once, though, as that Bonus Action.
Arcane Charge is pretty nifty.  Wreck somebody sideways, then teleport to another across the battlefield and do it again.  That's cool - I admit it.  Still feels like something's missing, though.
Improved War Magic - at 18th level, you can now cast a Spell (which you've been doing anyway, maybe), and attack ONCE as a Bonus Action.  FACE.  PALM.
*Not featured in the screen cap is a neat little flavor perk where you can call your weapon to you as a Bonus Action.  ...More on that later.

Talk about a lackluster reception, and it isn't for lack of players trying.
  The flavor text of the Eldritch Knight sounds like the BEST TIME playing as a Fighter.  The versatility of low-level Wizard magic and blasting power, and all the standard Fighter perks, plus more Feats than anyone else (so customization options).  I've had a few players go for this build, only to be sorely disappointed by the extra features, to the point that they RARELY used their arcane abilities, defaulting to vanilla fighter most of the time (you know, the one that can attack eight times in a round?).
So without sounding too verbose or long-winded, I propose the following adjustments:  

Let's address the first Treant in the room - War Magic is downright mean to the Fighter's primary ability set.  Just swap it around.  Change the language like this: "Beginning at 7th level, when you use your Action to make a weapon attack, you may cast a Cantrip as a Bonus Action."
  "But what about spells that have a casting time of 1 Action!?" I hear you scream.  
Don't care.  Sorcerers get Quickened Spell, Eldritch Blast fires multiple separate rays, and Fireball has been around for three levels.  Get over it and let the Knight swing their weapon into a skeleton twice and rock a Firebolt on the sabertooth tiger gnawing on your Cleric.  It's their job - let them do it.
  And later, just upgrade the Bonus Action to a spell of 1st or 2nd level.  Yes, you're effectively "quickening" those spells, but the Fighter still burns their VERY LIMITED resources in the form of spell slots.  By 18th level, they hold no ability to be a more effective Wizard than the Wizard, but they CAN hit 3-6 times a round and unload a Hold Person beforehand.  Don't lie to yourself, you WANT that on your side.
Side Note: if you REALLY feel like they should sacrifice more to get that spell off, have them lose ONE of their attacks.  But not more than that.

  These tiny adjustments I ensure will make your Eldritch Knight more effective, exciting, and FUN to play, while still honoring the spirit of its origin.
For every failed dynamic, I used to throw myself into a complete overhaul of a class or archetype, or worse, made my own; flawed and devastating in ways I could never have imagined - all in an attempt to fix what was only minutely broken.  Grace (and age) have taught me that subtle adjustments carry the most elegance, and truly make all the difference.  

There ya go.  Eldritch Knight to Eldritch King.
You're welcome.
​-Adamus

These proposed adjustments, though allowed at my tables, are indeed HOMEBREW.  Be sure to ask your DM for approval before utilizing them.

The monsters of Dungeons and Dragons sometimes fall into the swirling cyclone of the diametric.  Two sides of an arcane coin, unequivocally linked to one another.  Some grow out of opposition, while others are twisted transformations of one - a dark miasma of spitting fire and screaming madness.  
  With all my talk of pendulums swinging and balances shifting, my lens lingers on creatures of this influence.  They are fascinating to consider - beyond our stats and alignments, to explore the STORY of their nature and what gives way in the imagination's gates when you do.

  The white winged horses known as Pegasi soar through moon-touched skies, a vision of grace and majesty.  When glimpsed by mortals, they linger only for a moment, touching down for a drink from mountain springs or crystal lakes.  Intelligent and vigilant, any sound or sign from the local wildlife will send them back into the safety of the clouds above.

Born in dens of starlight in the realms of Arborea, the overwhelming positive good of a newborn Pegasus would spill out into the astral sky, alighting new stars and sending the nearby plants to bloom.  An equine marvel hatched from an egg, a Pegasus embraces flight almost immediately, its feathered wings glinting with astral efflorescence.  
  Pegasi nests are commonplace in Arborea, and the wondrous sentience of the creatures makes them loyal mounts to the Seldarine - the pantheon of Elven gods.  Faster and calmer than any wyvern, a Pegasus must be persuaded to serve their rider, entering a partnership that can last millennia.  The Seldarine will sometimes send Pegasi to the Material Realms to aid their followers or serve as messengers of their will, but depending on the forces in play, sending these faithful creatures has its own risks...

A visage of hellish terror, a Nightmare often appears in a cloud of roiling smoke, its mane, tail, and hooves wreathed in fire.  The creature's onyx form moves with a wraith's speed, vanishing into the night in a burst of brimstone.  
  Though it can be ridden by the occasional antihero on a redemption kick, the Nightmare is a prime mount for creatures of exceptional evil.  Demons, devils, death knights, and liches all call this fiendish horse a steed, and many more repugnant souls seek to claim their own by summoning one from the Lower Planes.  Thing is, if you don't feed that hell horse a worthy sacrifice upon its arrival, it has no reason to stay loyal to you.  A good many cultists have been burned to a crisp due to this small omission in the fine print.

This is where things get interesting.
  According to Dungeons & Dragons canon, a Nightmare isn't BORN, they are MADE.  It takes a dark ritual involving the torturous removal of a Pegasus's wings, the more brutal the better.  Literature is mixed, but the theme here is cruelty; the slower and more horrific the removal, the greater the Nightmare produced.  And this isn't a bait and switch situation; the Nightmare IS that tortured Pegasus, driven insane by brutality and dark magic. 
t's sick.  And I kind of love it.
  Because this relationship raises a few pathways that I want to consider:
First, the inner circle of the Seldarine would be indirectly responsible for the creation of a Nightmare in most cases, as these dark rituals often take place at the hands of mortals - or those directly tied to them.  To send a Pegasus as an avatar of the Seldarine opens them to possible capture through dark forces, perpetuating a dangerous silent war of astral attrition.  How insane to fathom an Archfey riding into battle only to come face-to-face with their old trusty mount, twisted by darkness and brutality.  
Second, the Nightmare retains the intelligence of Pegasus form.  This is no mindless beast bent to one's will, and though the rituals require sacrifice to link the mare to the rider, I would venture that a mental or verbal bargain is still required.  In fact, I could see the maddening steps of a certain ritual play out deliciously - fool a Pegasus into believing it is making a heroic pact and companion, only for the creature's true nature to slowly twist the poor being into its Nightmare; like a frog slowly boiling in the pot.  
  You're not breaking down a pet, you're convincing a sentient creature - this requires more nuance.  I like to think that every Pegasus has a name, a personality; hopes, dreams, goals, not unlike a heroic PC.  How does one twist and manipulate a hero into becoming a villain?  If the Star Wars prequels taught us anything, it was how NOT to portray one's turn to the dark side (sudden is bad writing) - what if this process could be more insidious?  Slow and manipulative, with a grand payoff.
Finally, the monster lore stated that the more brutal the shift, the STRONGER the Nightmare.  Which pulls me down the jackal hole.  If you have a particularly twisted or prolonged "ritual", could you create a "greater" Nightmare?  I'd imagine that Pegasi under the Seldarine would make names for themselves similar to their heroic riders.  Perhaps the greater the renown, the harder the fall.  Such a change might yield something along the lines of a Night Terror (or "Knight Terror"); the twisted mirror of a once great heroic steed.
  And if this is possible, could a Nightmare be redeemed?  Perhaps its flight is never restored, but its good nature and starlit white coat, with blue fire for its crest, restored.  What story could that creature tell?

As I research, I leave you with one more idea through the ether.  A Nightmare canonically can pass through the Ethereal Plane, carrying its rider and several others along for the journey.  Imagine what it sees in the mist of the dead.  Old soldiers failing to pass on?  The spirits of lingering beasts and the wisps of old sages?  Or do they see themselves...the Pegasus inside, a haunting specter of their past life. 
And does a Pegasus dream of its other possible lives?  Does its innate senses of fate and danger paint the picture of its dark future, its Nightmare, in cool reflections of mountain springs.  

The pendulum swings.  
Take care, lovely people.
-Adamus

A cursed mix of wings, talons, and a vampiric stag's head, the Peryton is a monstrous entity.  It is depraved relentless in its vicious pursuit to maim and devour the hearts of other creatures, holding a specific hatred for humans and elves.  Even injured, these creatures will hunt down detected foes, until at least one of them is dead.

Their feathering from a distance could be considered beautiful, and with wings tucked, settled upon the ground, the Peryton might pass for a lesser woodland being.  The moment one gets closer, though, you'll notice a good many things are off.

First, actually, would be the smell.  In this case, a lack of one.  Less sensitive noses would identify the creature as human, but those with a modicum of training or enhanced primal senses would pick no smell at all, coupled with an overwhelming sense of dread.  
  Standing over 7 feet tall, the Peryton's demonic stag face smiles with rows of razor-sharp teeth.  The plumage of their chest might tell you their gender (males tend to be blue, while females are a pale white), but soon you won't care.  Their antlers, jet black and harder than steel, are used to rend and impale, and their depraved form is resilient to all but magical weapons. 
As their eyes of orange flame pierce through the fog, any light that passes over them lies about their true form.
  For you see, the most peculiar element of a Peryton is their shadow.  This winged, evil beast will hiss before you, but its shadow will present as human.  Always.  Human.  

This oddity presents a plethora of curious theories, but few had evidence to match.
  Some Loremasters believe the false shadow to be an echo of the last creature the Peryton killed.  Given its penchant for violence against humans and elves, this was the prevailing theory for hundreds of years.  It wasn't until the haphazard findings of one Grenaldi Mayweather, a gnomish priest under the cover of twilight, who one night happened upon a nest of the creatures in the Ghastshadow Mountains.  She observed the flock tear into a pack of roaming Aarakocran, ambushed or set upon as they slept.  Just as history told us, the Peryton ripped open the chests of their victims, consuming the still-warm hearts with grim satisfaction.  Mayweather watched in dread curiosity, eager to solve the riddle of the shadow...  But the humanoid echo remained.  No winged shadows manifested.
  Mayweather was lucky to escape with her life, but returned soon after for more observation, this time with an elite guard to watch her back; the knowledge was too important not to be careful...

It would also be Mayweather that would witness the first instance of a Peryton being born.  Though there are documented family units of a male and a female Peryton (though they'd be hard-pressed to care for their young, if not kill them), this instance within the nest involved two females.  
  Both left to hunt, smelling blood on the wind.  They were gone for hours.  When they returned, blood dripping from their claws, they delivered several chunks of flesh to the next to feast upon, and a still writhing human man!  Mayweather watched as her lookout - a young brown-eyed ranger - was clutched by one of the pair and pulled toward the other, like it was presenting a gift.  Firey smoke and twisting gray tendrils spilled from the one in waiting, before its teeth sank into the man's chest, ripping his beating heart from the cavity.  His body went limp, and Peryton female scarfed down the heart, her eyes shifting translucence in the penumbra.  
  Then Mayweather heard a sound that sent chills down her spine.  
Like an echo of a child's laugh.  A giggle in the gloom, small and innocent.  Then it grew, warping and dancing along the walls, raising in pitch and warble, until it is a chorus of cackling.  The other eyes in the nest rise and join in, their necks convulsing and twisting backward with the sound, a malevolent inversion of mirth and satisfaction.  The sound becomes a beast in and of itself, a roiling mass of whoops and hollers, striking chords and stark dissonance.  Vibrations spill out the mouth of the cave, whispers at the ears of the hidden spies, and shouts upon the walls that surround them.
  The guards around the gnome begin to clutch and claw at their ears, the cacophony bringing a few to tears.  Mayweather instinctually covers the sob of her closest ranger, insisting that he get himself together.
Then.
Silence.
  The smell of dread hits Mayweather's nostrils as she dares to peer into the nest.  All the Peryton stare straight ahead, their mouths gaping open - a frozen, terrifying smile.  Until they all snap their eyes...to her.

They made it out with one casualty.  Her second blue-eyed scout, snatched by a rogue talon before he could slip into the wooden door of a magnificent mansion.  
  Safe within the dimensional space, Mayweather vigorously wrote down her conclusions:
1. New Peryton are born by a female consuming the heart of a freshly killed humanoid.
2. Their shadows flicker into monstrous forms during the process of incubation.
3. When incubation begins, nearby Peryton gain heightened senses to protect the pregnant female, becoming even more violent.  The more there are, the stronger the pack's senses.
  Her fourth note she added weeks later, when her guards - while out hunting - were set upon by a pair of Peryton, seemingly tracking them for miles.  When they finally confronted the creatures, they were surprised to see two young Peryton, newborns - one with brown eyes and the other with blue, both with shadows of human form.  ...Felling the creatures was tough, but much worse for their psychology.  Poor guys.
4. Newborn Peryton share the eyes of the creature whose heart they were born from.  As they get older, and kill more for their own survival and pleasure, the blood tarnishes the eye color, shifting it to match the orange-red of the others.

Mayweather and others theorized that the first Peryton was a cursed human or elf, twisted by a god of chaos.  The bards of old expanded upon this, marking its origin to infidelity, curses, and carrions feasting on cursed corpses.
  Given Mayweather's most recent expeditions, however, the clearest line exists through pure vehemence.  These aren't cursed humans - they were MADE by something.  Sometime in the first age, when great magics could be wielded by mere mortals, a wizard general - whose name is lost to time - sought a tactical edge against the elven and human alliances.  So he juxtaposed what he had on hand with fiendish blood.  An intellect unmatched, the alchemist rivaled the gods for a moment - before his heart was ripped from his chest...

Mind the shadows.  Watch the skies.
See you next time.
-Adamus

These little buddies are so intrinsically in tune with the magical world that I have taken the liberty to codify a few with magical persuasions of their own.  Sure, you'll have the standard pseudodragon flapping around your nooks and crannies and old libraries, but if you dig deep enough and scour long enough, you'll undoubtedly run into one of these variants.
  Illusory - Pseudodragons don't have a specific language, instead communicating telepathically simple ideas.  Those that are steeped in illusion magic has found a way to interpret the innate basics of their school to help communicate better, manifesting in a sort of "thought bubble" above their heads communicating more intricate picturesque ideas.  I just love the idea of a pseudodragon with an ellipsis over its head as it ponders, and then watching it blip back and forth between steak and its studies; the ultimate SQUIRREL moment.  :)
  Evocata - a little friend who spends a lot of time around battle mages and explosives can evolve into a combustion dragon.  Highly emotional, passionate, and excitable, an Evocata will manifest its core magic in explosive bouts.  Get too excited?  Fireball.  Or Fog Cloud.  Or Plant Growth.  Get too sad?  Cast Darkness.  Get protective of their master, their binky, or their new bestest friend that they've known for five minutes?  Ray Of Frost.  Or Finger Of Death.  You know, TOTALLY NORMAL reactions.
  The list continues, and I have a feeling the more I play with this concept, the more hilarious it will become.  Does a Cleric use her Pseudodragon as her own personal lie detector because it's infused with Divination magic?  Does a diplomat use his to win over a crowd because he steeps in Enchantment?  The possibilities abound!  
(and now my players know...good luck)

See you at the table.
​-Adamus
  

I've been running campaigns long enough that I've stacked up NPCs like Pokemon cards, ready to unleash them onto unsuspecting players.  Sometimes they work wonders, other times they suck wind through a straw.  Let's take a look at a few and see what I could have done better.  

Core Concept: Jedrek is a one-man army.  Built by a broken monastery as a final solution, a Blackweave monk wields the power of the broken weave.  Using his skin as parchment, a Blackweave covers himself in arcane runes and tattoos, each connected to an ancient power.  By engaging a tattoo, he can cast the spell that was inscribed upon him, wielding the cosmic powers of the lost tribes of wizards.  But once the tattoo was spent, the ink burns off of him, lost forever.
  A Blackweave can add permanent augmentations to his body by inscribing runes upon the skin, and burning them over 100 days.  These marks become infused scar tissue, sewn with residual power.  One can use this technique to add extra ways to manipulate their Ki, make their bodies more formidable, or make their minds sharper.
Version 1.0: A Way Of The Long Death Monk at Level 17, with a Level 14 Gunslinger as backup VS a party of five level 10 adventurers.  Low Con saves and lucky rolls on my end put the melee friends on the stun train pretty fast, but things got pretty close.  A Tattoo of Contingency - Revivify was placed on him as a last resort by his Compendium (the order branch), which saved his skin.  Using Step Of The Wind, he escaped, healed, and returned for his quarry, killing a PC and taking the body. 
  Notes: It was a tough encounter and a decent field test for the build, but he didn't use a lot of his tattoos.  As it stood, his action economy required use of his Bonus Action to engage a tattoo.
Version 1.5: The players, now at full force: 10 characters at Level 13 VS 1 Level 18 Long Death Monk.  Taking no chances, the resident pyro cast instead Telekinesis, holding Jedrek aloft and restraining him.  As Telekinesis is a contest of checks, not saves, Jedrek's Diamond Soul (proficiency in all Saving Throws) doesn't engage.  Good job party!  However, because of one small wording technicality in Jedrek's build language...he wasn't entirely shut down.  He still had access to ALL of his Weave, so every round he'd struggle against the Telekinesis (fail), then spend a Bonus Action to engage a spell that was laced onto him.  It was a "chip damage" fight; still interesting and dangerous, but felt off somehow.  It also took a long time.  They killed him and burned the body (evidence), and felt good about avenging their ally.

Future Adjustments: We finally figured out what was bugging me.  Engaging the tattoos can still be a Bonus Action, but I propose a few limiting factors.  Certain on 1 and 2, entertaining 3 and 4.
1) He has to touch the tattoo, which requires movement.  If he's restrained, he can't do that.  Telekinesis should have shut him down completely.  It's the anti-monk spell!
2) There should be a Ki cost to engage the spell.  Either Spell Level = Ki Points spent or 1/2 Spell Level (rounded up) = Ki Points spent.  Cantrips are always 1 Ki Point.
3) I'm considering a spell level limitation.  Like no spells above 7th...  Then again, even with a 20th level monk, using 9 Ki to cast that crazy Meteor Swarm that others at my level can also crank out ...as a Bonus Action...  Yeah, no.  We're limiting this crap.  No 8th or 9th level spells.  7th I MIGHT be okay with.  We'll play with it.
4) The Runes he's burned take up attunement slots, or 1/2 an attunement slot.  They take a lot to get, including cost and training (100 days, remember), but they *are* permanent; so someone with a lot of time and resources can add on Runes easily.  They already have a maximum of 3 Runic Augments before their body can't take the strain anymore, but after that we've got Bracers of Defense, a Ring of Protection, and a Cloak of Protection (a total +4 AC, and a total +2 to all saves).  With Runes that make your Martial Arts 1d12 (instead of 1d10), allow you to Hunter's Mark, and others that grant you Sneak Attack for Ki...  Don't want anyone to get too beefy too fast.
Why?: Action economy is too far broken.  He can be a better wizard than a wizard, and still PUNCH REALLY HARD.
Is the Blackweave dead?  Nah.  But it requires more tweaking as a subclass.  Monks have A LOT of options already, so it may serve better in another class (Ranger could be interesting), open-ended to all classes (needs some secrecy), or needs a few more limitations/refinement.

Core Concept: The Daughters of Syn had been a consistent villain group all throughout campaign 2 on Tuesdays, and I'm a big fan of using common mythos and turning it on its head.  In this case, we're using the Seven Deadly Sins as our model.
  "Sly" is Sloth.  Laid back and lazy, this knight doesn't want to do much, instead opting for her familiar, Freya, to do most tasks for her.  But for all her laziness, if ever you were to hurt Freya, or try to hurt her more severely, she would finally show you her true power - frightening and efficient, she'd like to end the fight as soon as possible, so she can return to her nap.

Encounters and Impressions:  Sly was my absolute favorite side villain.  Every moment the party encountered her, they fell in love with her dry wit and lack of commitment.  She would often show up on the outskirts of a battle (showing that she was always watching for her mistress, Syndrosa), smoking a pipe and giving raucous commentary of the fight, quick to crack jokes or just shrug at veiled threats.  In fact, the first time she met the group, she helped most of them escape the Underdark (I wonder if that endeared her to them a bit).  She was really just gathering information on them at that point, but she really didn't care either way, so killing them would be boring.

Fight 1: The first real encounter with Sly involved the group trying to rescue a little girl trapped in the Underdark.  Sly had an amulet on her person with a soul trapped inside (but the party didn't know that, only that she had a nice amulet, it looked valuable).  The party turned into bugs and snuck into her room, while others tried to deal with Sly's partner, an Oathbreaker Paladin named Naz (Pride).  For most of the fight, the party simply kept Sly occupied as she played with them, always at the edge of caring.  It wasn't until Naz was killed that Sly began to show her true ferocity.  Sly's first boon involves Freya; the fire fox fuses with her form, granting her lycanthropic strength and speed, as well as some Greater Invisibility.  Couple this with the fact that she's already a Level 16 Druid by now...and we've got something serious on our hands.  The party has A LOT of close calls, but manages to kill her, her form crumbling away in strips of...ice?

Fight 2: MUCH TIME PASSES and the group assault the now Queen Syndrosa in her OWN LAIR, and are promptly defeated.  Despite this Full Party Capture moment, the players were SO HAPPY to find out that Sly was indeed alive, and the version they killed was some sort of Clone or Simulacrum.  Heck, she even helps them escape the follow-up encounter (again: she doesn't really care).  But upon returning to the Fortress of Syn, now better prepared and after taking out Lust and taking some weapons from Wrath, they come across the real Sly.  She toys with them a little...and then the Paladin kills the fire fox.
  A Storm of Vengeance, and A LOT of near-death experiences (2 deaths total, but yay Revivify), a well-timed Power Word Kill drops Sly for good (strange, she could have totally Counterspelled, but she didn't...).  The party was the SADDEST I have seen them after this fight - they didn't want it to end!

Build and Boons
Class: Druid 20, Circle of the Moon (not that she cares)
Standard Boons: Boon of Fortitude (HP +50, Temp HP Ward +20), Boon Fey Step (Movement +30 as a Misty Step)
Boon of the Fire Fox - grants the Knight a familiar in the form of a fire elemental.  This familiar can heal you from a distance and merge with you to grant extra physical bonuses and a burst of fire damage at the end of every one of your turns.
Boon of the Sloth - Aura of Relaxation (little things don't stress you out, Calm Emotions at all times, advantage on saving throws against being charmed).  Social power of Disarm (disadvantage for foes to resist your relaxed charm).  You have entertaining and informative visions involving the people you observe; you no longer sleep, but napping opens these visions to your perfect memory.  Whether you act on them...is totally up to you.
Is Sly gone for good? - Mmm.  Tricky thought; death can get weird in D&D, and resurrection moreso.  Depends on where her soul ended up, and who cares enough to get her back.  I have a feeling her return would not be an unwelcome one, at least by a few PCs. ;)

Core Concept: A Circle Of Spores Druid hell-bent on conquering the world of beasts, controlled by the Mantle of the General; an ancient artifact forged by the Erlking of the Feywild.  Woof.  That's heavy.
  Anox was a product of the Erlking's choices; after the Archfey took the Helm of the Hunt, his purging Valkyries decimated the forces of Anox's predecessor, Gurlanik, the Fade.  To rectify this, Anox used his only son as a lure to other beings touched by Fey energy, and used his Circle to "seed" them with necrotic powers - and his control.  The resulting Treant-Hybrid army, coupled with the stolen Mantle's innate power to call nearby beasts under his command, Anox began preaching dominion over the Wilds beyond and amassing an army of druids who shared his ideals.
  His son, Darius, finally fed up with the loss of innocent life, formed his own pack of druids - attempting first a coup, then, when that failed, an all-out-assault upon his father, while freeing those that would be hunted for his dark purpose.  This betrayal marked the beginnings of Anox's madness, and the Mantle began to wrestle control away where it could.  Soon, the two entities became indistinguishable from one another, and the more Anox used the Mantle to augment his magic, the more it took from his mortal body...but he could not die as long as it was bound to him.

Boss Fight: This fight was...problematic.  There was a spore lair with infectious actions, a whole one on one duel where the PCs made strange tactical decisions and then got mad when they didn't work out.  And this was already a difficult campaign to run; huge mix of experience levels and play styles clashing all over the place.  If I were to run this in the now, 4 years wiser, I'm confident it would have been earned.  Honestly, I was still cutting my teeth on this one.
    There were personal stakes with a PC, which, in any other case, would have made this much more charged - the end result here...was confusing.  Misinterpretations of rules and descriptions, intentions, and flow; it got pretty awkward at times.
  What I WANTED to happen was a dynamic battle of shifting landscapes and status effects, a ticking time bomb of spore growth, and a possible moral quandary of tearing the mantle free to destroy it or don it yourself.  Instead, it was a jumbled mess with a few great moments (I'll give that to my seasoned players), tarnished by that constant confusion or rules-lawyering.  Different group, different time I guess.

The Build: Druid 18 [Circle of Spores], Warlock 2 [Great Old One*]
  The Warlock element of this build required a lot of homebrew.  This Great Old One ends up being the Mantle itself, a semi-sentient immortal object (one of my "Legacy Artifacts") that has held many hosts before, and draws power equally from the Shadowfell and the Feywild.  It had regenerative properties, negated by radiant damage, and the Mantle has its own suite of innate daily spells - it could even cast additional spell effects by placing levels of Exhaustion on its user.  
  At the time, I wasn't confident with custom Legendary Actions, but a second go would simplify Anox's action economy to that of a standard druid, and the Mantle would act with Legendary Actions of its own, illustrating the dichotomy of the two entities joined.  I could then drop better hints as to the artifact's nature, and I would allow the PCs to attack the Mantle directly, adding a puzzle to this duel of fates.
  As it stands, Anox - and myself - learned a lot from this boss fight, and we haven't seen the last of his character.  Perhaps a new version will retcon the old for us all. 

Anywho.
It's important to look back now and again.  To consider where our lessons lie, and what new adventures we can craft with them in mind.  Maybe I'll do this again - I've got plenty stashed in the mental basement.

If you enjoyed this, maybe say so, or check out the Patreon (it could always use some love).  
Stay warm out there.
-Adamus

Pulling our visions into messy arcane studies, pits flanked by dangerous ooze, and dark caverns of mystery, we rest our eye upon one of my favorite little critters in this whole game.
  Sporting leathery skin and angry spikes, with claws for climbing, and a mouth often gaped, the Nothic is unnerving on its own, but its enormous, unblinking eye sets it far apart from its other cave kin.  Despite its stark appearance, though, the Nothic can form rich bonds and motivations, even spilling themselves into an industry all their own.

Like I said, the Nothic uses to be a spell caster - a creature devoted to the arcane.  This means that those cognitively aware enough of their own affliction would seek to remedy it.  Which births Nothic alchemists and artificers, brewing elixirs and constructing shadows, seeking to silence the incessant voices of their fragmented memories.  
  For those who drink the ill-made elixirs, further mutations plague their forms.  Orcish blood infuses their body with resistance; devilish magic turns their blood to smoke, their steps to shadow; Fey magic infuses the spines and spurs with wild magic that explodes with their emotions.
  On the other side, the unhinged artifice breathes new terrifying life into their visage.  An extra set of arms of offset their twitchy nature; electric infusers to inject them with strange mutagens, all the better to defend their workshop from intruders.  If you were driven to mad industry to silence the voices in your head, what would you make?

See you at the table.
-Adamus

It happens every once in a while.  You're moving and grooving in a campaign, joking, laughing, having a blast - then the big bad shows up and things go sideways.  They're tough, but you do your best, and the dice are all over the place.  Characters are dropping left and right as they pull out all the stops to win, and the rival group's preparation throws the party off-guard.  Then the tides begin to turn, and realization sets in - your players are going to lose.  
  HOW that happens, though, and what it means, is up to everyone at the table.

In my Feywild campaign, there has been a consistent air of hilarious strangeness and dark undertones, with a side salad of irreverent quips and bonkers magic.  At the table, we find our sweet spot in Social Interaction and Exploring this intriguing setting, while building up a network of knowledge on the many forces vying for control of this magical realm.  Our best sessions are derived with zero combat and an army of NPCs to talk to and mess with.
  It's in Combat and conflict that the veils struggle, and the dark side of the setting pulls into focus.  
This is a High Magic setting full of Fey and wizards and chronomancy and Queen Mab.  Campfires sing to you, trapping those entranced in an endless dance of death.  The grass needs compliments or it will kill you.  The dreaded Theater looms in the dark forests, luring unsuspecting travelers into its immortal troupe.  And the evergreen kings and queens of this realm care little for the fleeting lives of a few amusing PCs.
  This means that when clashes happen, there are often elements of chaos that are hard to predict.  That said, that was one of the selling points of the campaign.  A "wild" version of magic and mischief that can swing some things in and out of your favor, but never too far as to push your success to pure luck.  A voyeuristic Archfey that finds the actions of a PC intriguing, and grants them a mote of possibility.  A character's plant affinity granting them transport across the map.  Pockets of void magic that provide inverse effects of certain spells.  
​  But in Combat, the dice can add a variability that can sometimes be less hilarious, and more tragic.
  When my party is frustrated, I am frustrated.  When they are sad, I am sad.  When they struggle, I struggle.  I am not a DM that supports adversarial gaming; it is not a "DM vs Players" mindset over here.  Do I challenge them?  Of course!  But when they're feeling it, I'm right there with them.  I WANT them to beat my big bads; I want them to win the day, so when they don't, I feel like I lost too.  And I don't want them to hurt, I want them to feel energized to return.  They didn't sign up for a trauma center EVERY week.
  Hmm.  Let me get into this a bit more so you can understand where we're coming from.

  The Feywild Warriors have been trekking around the Ionian Feywild for 12 levels now.  We do milestones, and they tend toward less combat and more interaction.  They're lovable children, when you think about it, as most of the PCs are around 17-19, one doesn't even know his age, and then we've got an old fighter into his 50s that acts like their dad (found family, you get it).  We've got a Dragonborn Fighter (Terhune), a Werewolf Druid (Buddy), a Tiefling Wild Magic Sorlock (Bry) and her elemental familiar (Soot), a Tiefling Bard/Fighter (Akita), and a Human Battle Master Fighter (Taman).  Because they're so dang adorable and well-intentioned, they've accumulated quite the entourage of NPCs.  Alannah - a Paladin/Tempest Cleric (wife of Taman); Essian - a half-elven War Mage, Alannah's ward; Vali - a human Rogue and now girlfriend to Akita (she went to the Feywild to find Akita, so that's love); Broty - a young Tanarukk (who has imprinted on the two tieflings and views them as little sisters)...poor guy has an intelligence of 5.  
  ALSO, along the way, they have happened upon another adventuring party led by a character they presumed killed in their first adventure.  A bridge guard who survived The Massacre Of Sentry at the hands of a Black Knight and joined up with another party to help him seek righteous vengeance.  His name is Jenkins Carpenter, or Jink for short, and he is avenging the death of his brother, Leroy Carpenter (yes, I am that guy).  Jenkins is joined by Nessa, a High Elf Ranger/Rogue, Remy the Lizardfolk Barbarian, and Sloan the Dwarven something (seriously, I don't think he knows what class he is).
  This literal army of deadly kittens have built powerful bonds between each other as they navigate the dangerous wilds of the Fey realm, each strengthening and redefining the odd family dynamic of those that face threat together.  All the while, dark forces move into position.  The Winter Court has occupied the City Of Astrazalian - a neutral ground between the Fey Courts - and is using it as a military position (that's not okay); an orcish army led by a tiefling warlord marches on the West; a gnoll army marches Northwest (and threatens to clash); the stars (spirits of guidance in the Fey Realm) are falling from the sky and being collected by the Whispering Rock guild and their seemingly corrupted leader, Montblanc (doesn't help that Terhune, Taman, Alannah, and Essian were all once members of this guild, whoopsie)...  And all of this seems orchestrated by a small group of individuals that call themselves The Four Gears.
  The party has had fleeting encounters with each of them.  
Hush, the Black Knight/Silencekeeper - the first real threat the party saw in their inciting incident on a bridge.  Simple stuff; they all met, hung out, antics ensued, they went to bed.  Woke up and the bridge town was burning down, and this jerk was coming through killing folks.  They tried to distract them, but the bridge collapsed, and now the Black Knight haunts their nightmares as they catch drifting news of their exploits.
Albrecht, the Kingslayer - a cleric of multiple gods (it seems), the party has mostly witnessed the aftermath of Albrecht's handiwork.  The guy has a huge distaste for small fey, burning spryte villages and darkling conclaves to the ground.  In a way, he's been knocking out lesser leaders to pin focus on larger forces.  He is surgical and pragmatic, but his true intentions are unclear.
Eon, the Kingmaker - a silver-tongued lavender tiefling wizard of deep knowledge and cunning, Eon has aided the party in navigating the gnoll army early in the campaign, but he has only become more creepy as time goes on.  He took a liking to his fellow tieflings, but holds no love for other races.  Seeing the growing power in Bry and a possible kinship, he has been invasive in contacting her, much to the worry of his fellows, even going so far as to bind himself to a promise not to kill her companions.  A promise that may spell his undoing, but it is entirely possible that he is playing a different kind of game.
Arameis Salfurion, the Whisper - an aasimar of unknown origin, this entity is known only through word of mouth and fleeting visions before death.  Most recent word has it that he serves as a consultant to Montblanc and his guild, and may be behind the collection of Fallen Stars.  He has been seen as an after-image of a Contingency spell woven into the symbol of the Whispering Rock Guild - set to turn people to dust if they broach certain topics of discussion.  Luckily, Alannah and Essian's abjurative abilities tipped them off before it was too late, and Taman and Terhune had already forcibly resigned.

In the Ionian Feywild, there are forces that serve as great equalizers.  None are more powerful or resolute than the Erlking and his Wild Hunt.  He is appointed by the Stars, so his legend is known among the denizens of the Fey far and wide.  He holds no Court of his own, though many claim to be of it.  In truth, he calls the honored dead to his banners - ancient Eladrin warriors culled by his Hunt in days long past and sworn into servitude to wash the realm of dangerous chaos.  He and his Hunt are the last bastion of defense and the grand hammer that allows the Fey Courts to sit on their thrones and raise their goblets in indifference.  In other words, if crap gets real, the Erlking will take care of it.

  Thing is, the stars are falling and war is brewing, and no horns of the Hunt are blaring.  The Fey Lords and Ladies are only mildly concerned, as is their way, but the lesser fey - like the extricated Autumn Court, or the Darkling clans - know that something is wrong, and that they'll be hit by the brunt of it long before Summer feels a tickle.
  Though they be young, the party has heroes in it, and those that lack heroics still garner a sense of justice.  There is wrong happening around them, and though they often move on to their next adventure, the wave is catching up to them - threatening to drown.  They conclude that they have two real choices: 1) Get someone to plane shift them to the Material Plane (where most of them are from), cozy up at Taman's house with his wife, get adopted, and wait till this all blows over; or 2) locate the Erlking and his crown, so evil can be stopped.  
  Prepared for both outcomes, I did not nudge a thing, but the group voted - option 2 was the way.
So they ventured to the savage dark forests of The Fading City, seeking an audience with its undead Fey Ranger King...Lord Calenon Thrayn.  Turns out, two armies also threaten to converge upon the city, so the party must sneak past in order to get inside first.  Which, they just barely do so, as orcs begin to pour into the city hot on their heels.  Luckily, the city has a defense mechanism: the Fog Of Purity.  Creatures that pass into this Fog undergo strange, random trials that measure a piece of their soul - some are straight forward, some are outright weird, and in clear Feywild fashion, it's pretty random.  Long story short, a few of the smarter captains emerge from the Fog deep into the dark forest that permeates the city...knee deep in dinosaurs and gigantic beasts.  Our heroes, however, emerge before a guide - a little Fey kitty - that leads them to Thrayn.  

  Much discussion later, we discover that the Erlking's Crown is hidden in the Material Plane.  As part of Shinealestra's lore, the city will phase to the Material Plane every night at midnight, its forest of nightmare creatures becoming a prized hunting ground for only the bravest of hunters.  It returns to the Fey Realm at first light, at dawn.  The castle flips, our resident human Taman and his wife rejoice at seeing a normal sky and normal grass, and the army of squirrels is led by a pack of sentient mushrooms with messenger bags to their next destination.
  After a clutch phantasmal force on a nasty T-Rex, the original party plus a Jenkins makes it through just before the cave mouth closes, leaving their allies to fight the dino.  Trusting each other, they have a chat with an Elder Being, get a very needed Long Rest in a time bubble, and push their way into a teleportation chamber.  The werewolf, rocking his child-like intelligence, bounds through the portal before the others can stop him.  He is seemingly atomized (think Dr. Manhattan, you weirdos), and while the players at the table contemplate if I just killed a character, Bry notes that the transportation runes have been tampered with.  Conclusion - they still work, they just don't go to the right place.  Four fragmented sendings and a lot of swearing later, Buddy returns, Bry fixes the portal, and our Taman has the brilliant idea to scan the area with a See Invisibility item.  Good thing, too, as Eon's voice creeps into our Sorcerer's head, and they watch him drop into the fixed portal, before they all jump in after him.
  They feather fall down into ruins; gravestones and sarcophagi overgrown with moss and fallen trees.  Bry's nature affinity clears the path to a throne, a skeletal guardian, and a crown...before urging everyone to look up.  Eon, silhouetted by a dark sky, floats above them.  "Thank you for showing us the way..."  He summons Minute Meteors...and detonates the Delayed Blast Fireball under their feet.

I crafted this particular encounter without a clear idea of how it was going to end.  Not that I've ever shunted PCs into certain positions to reach a specific outcome, but sometimes you can foresee the three basic endings in a battle.  Get to know a party well enough, and you get a pretty good idea how most things are going to play out.  But this time, there were certain variables that made things tricky.

1) THE DICE WERE BEING JERKS - I award inspiration, give advantage where I can, and overall support my players given the wacky setting we all agreed to...it just wasn't helping!  Saving throws getting botched, attack rolls whiffing, amazing ideas with simple checks falling flat.  On both sides!  And, you know, maybe that's a good story, too.  This is a group that buys into that variability; I like to think we're charging up for those legendary three Nat 20's in a row moment.  (it's happened, let's let it happen again).

2) THESE ENEMIES HAD TIME - They have been plotting, preparing, and hiding.  I can't spoil a lot here, but their abilities are based on rules, magic items, and preparation.  They are a counter-party, and this is their moment.  They had a plan.  Eon shows first and distracts while Hush goes for the crown, and the third waits in the wings for the most opportune moment.  They are smart - flawed, but we'll get to that - and deadly.

3) THEY'RE PUTTING IT ALL ON THE TABLE - This being such a clutch moment for The Four Gears party, they're going to burn a bunch of resources to achieve their goal, making them LOOK very powerful for a limited time.  IF our heroes can hold out against that onslaught, that's another chance in the PCs' favor.

4) MANY WAYS TO "WIN" - with an Ancient Artifact in play, there are a plethora of ways this could go down.  We just finished a segment where at least two of our PCs saw visions of themselves wearing the crown, so we know it's possible.  Holding the crown has one effect (it can't be stowed in a container, btw), while WEARING it has another.  On top of this, despite Eon's destructive forces, his connection with the party can be exploited; whether that flips him to the other side or pisses off his companions enough to cut him loose, that's another win in the PCs's direction - he DID make a blood pact not to kill them.  Throw in our Amplified Wild Magic (Feywild custom), a reluctant warlock pact, burgeoning tiefling rage powers, our Taman's random ability to nullify certain magical effects (I have to roll for it - dice were jerks, see above), and a custom druidic circle all about ripping and tearing, and there's a surfeit of possibility here.

Woof, friends.
  This was tough challenge against prepared, patient enemies.  And for a PC party that has done pretty well flying by the seat of their pants into most encounters, I foresaw that this could be a tougher go this time around.
After eating the explosion, the party scatters while Eon attempts to place Bry into stasis - keen to remove her safely from the fight.  Taman, in a cool reaction that I will allow, pushes Bry out of the way, and becomes inert for a round instead!  Meanwhile, the perception-level-stupid-high Buddy notices that someone invisible might be making their way to the crown.
  Akita decides on her own to polymorph into a super fast, super squishy bird and bum rush the crown.  An invisible Hush cuts her out of the form as she flies by, but Akita maintains her momentum to land on the throne, hands already on the crown.  With Jenkins and Buddy sprinting to help (the natural 2 on Jenkins's acrobatics did not help), Akita weighs her life choices as the skeleton wriggles to life and begins to wrestle with the tiefling to keep the crown.
  Hush, now visible, puts on full display the completely legal and totally unfair mechanics of the Echo Knight and proceeds to tank a clutch polymorph (on an Echo), phase from one Echo to another, and one-shot our resident NPC Jenkins (who's just trying to avenge his brother, my guy, come on now!) with a Nat 20 great sword + sneak attack.  With Jenkins making death saves in front of Buddy, Hush cleans her blade and silently squares off against our druid.
  On the other side of the battlefield, Bry begins to show just how much she's grown as a mage as she not only deflects blows from Eon, but shatters his wards.  The surges of Amplified Wild Magic elevate stones around her, and continue to build up inside her, threatening a cataclysmic burst.  Terhune hides, and does his best to stay hidden while taking sniper shots at Eon.  Both, due to obstructions, are unaware of Buddy and Jenkins's battle, nor are they fully aware of Akita's predicament.
​  Akita wrestles the crown, and the skeleton guarding it, off the throne.  She does so with such primal force that the throne, its pedestal, and the plinth of stone it rests on, slide free in a shower of stone and dust.  In the debris, a focused Akita pulls the crown free, its desiccated husk filling with new florid life and personality akin to her own.  And crawling from the opened tomb under the throne, are the honored skeleton guard of the Erlking, watching their potential queen eagerly. 
  Whether by fear or force, Bry pushes Eon further into the ruin, and he doubles over in pain in the air; the arcane agreement he made threatens to be broken, so he sends healing words to Jenkins as Buddy rushes to help Akita (and more skeletons rise around her).  Hush shifts her Echo closer to a hidden Terhune, and finally Taman has someone to fight.
  Without structuring the rest of this in a play-by-play, a few things happen in quick succession that turn this whole thing sideways:
1) Bry's Wild Magic begins to manifest in telekinetic ways, flinging terrain across the map (one of which knocking Hush prone, to Taman's delight).
2) Hush shows her hand by raging, and a real threat comes into play, one that hits exponentially harder and is way more difficult to wound.  ...But at least she's finally HAPPY to have an opponent worth fighting.
3) Eon's arcane agreement begins to debilitate and damage him the more hurt the PCs become; his allies do not share his values.  The lavender tiefling becomes so overwhelmed by Bry and maintaining his arcane deal that he fails his saving throw to not become Entangled in a terrain hazard, and a few more failed saves later, becomes a sitting duck for the enraged Sorceress.  ...So Bry intentionally devotes her resources and ire to immolate Eon, but not before he relinquishes his Staff Of Balance (Chronomancy) to her, somehow happy that she is the one to kill him.
4) At the precipice, the Skeleton Guard ache for a choice, and Akita hesitates.  Instead, Buddy makes the decision FOR HER, forcing the crown onto her head.  Her wounds disappear, the Skeletons bow, and her sight opens to the hundreds of spirit warriors now at her command.  This transformation takes time (3 rounds), and she can interact with her growing powers each turn, but again, it takes time.

The Feywild is a land that, on the surface, might appear more silly than serious.  However, the consistent theming of this campaign yields specific truths of the setting.
1) Fey and their realm are mischievous, dark, and often twisted entities who care very little for the mortal coil.  Just because it looks nice, doesn't mean it's safe.  Even the "jokes" of the Fey can be deadly. 
2) Magic, though not at its most raw, perpetuates all living things here.  So, weird stuff abounds, and it's pretty common.
3) There are rules, and they are numerous, for navigating the Fey realms safely; but many do not know them, and they often change dependent on a plethora of factors.
4) Fey and their ilk are often unreliable narrators, choosing interpretation over hard facts; this laces their words and veils their intentions - a true Theater Of Life.
5) Study of this realm yields immense power, but it requires extensive time, focus, and energy.  Even a little bit of digging reveals the dark tone beneath the whimsy (consistent from the beginning of the campaign).  ...we just really saw this one, this time.  :(

  It was stated before that this group has done quite well just stumbling through.  Sometimes the PCs plan a little here and there, but mostly they do exceptional when they fly by the skin of their teeth.  These PLAYERS are top-notch; they bring vibrant expression, creativity, knowledge, and joy to the table, which only deepens our collective world, and they PAY ATTENTION, no worries.  And all have expressed that they brought creatures to the table who are "inexperienced" in at least one important skill each.  Good!  This found family has done amazing things in the face of overwhelming odds - by luck, creativity, allies, and pure unadulterated pun power!
  And now.
This is the first time that they were unsuccessful, in the traditional sense.  The bad guys "got away."  One of the party is missing, another is dead (but not for long!), and the others are grappling with their decisions - some made BY them, others made FOR them.  From the DM's side, I offer opportunities for choices, but the distinct choices are specified and executed by these veteran players.  They are organic, in the moment, sometimes snap character decisions.  Which means, another reason why I love this party, we now have a huge opportunity...
We get to DEAL WITH THOSE DECISIONS.

Every character in this party was struck down in this session.  Whether it be the very real severing of physical mortality, or the denser psychological dread of vengeance, or the helplessness of being a human in a world of fairies.  For many, this could be described as their lowest point.
  It can be a rough place to be in as a character, let alone a PLAYER.  Several members have talked openly about the "mistakes" they made during the fight; things they could have done differently if the dice had cooperated; musings on certain game mechanics and gear load out...  And yet, each came out with a plan to process this experience.  Maybe we take some extra time before our next session, but we WILL have another session, and many more after that.  This story WILL continue.  Where it goes, is up to us.
In all great stories, especially ones that we share, this moment occurs.  Some hit it harder than others, but they share the same term.  We have entered The Abyss in our heroic journey.  It is the space diametrically opposed by our Call To Adventure (our first few sessions).  Often this is a Death and Rebirth - for some, perhaps more literally than others - and what comes next is a Transformation; rising action, rebuilding momentum, standing back up with lessons learned.  
  Initially I was concerned with the low energy post-session.  With so many mirthful games under our belts, it felt WRONG to end the session like that.  I became obsessed with the idea that I had led them astray; wounded them somehow.  And what we all needed was a little extra time to process the events, and hatch a plan moving forward.  What we've done, at last, is setup an arc for just about everyone.  Our innocent, fun-loving Sorceress just straight-up murdered a dude (he was probably bad news, but still); our werewolf is Lost In Space, dealing with the guilt of putting the crown on Akita; Akita is grappling with being robbed of her choice, and yet craving the crown for the good it could do; Terhune, literally dead, drifts through his Ethereal past as his body and soul are reconstructed anew; Jenkins sits in silence, feeling weak and a waste of space, completely unable to enact his vengeance; and Taman, the old fighter and tactician, the hero of this story and the glue of this group, couldn't protect his adopted family even if he tried.  
  That is an Abyss.
And, as anyone who has struggled their own depression knows, the first step out of the dark is the hardest.  But with every step, you will be stronger for it.  You will stumble, you will learn, you will heal, and you will keep moving forward.  

This time: Death (close Phase I)
Next time: the steps toward Rebirth. (open Phase II)

See you at the table.
-Adamus

In 5th Edition Dungeons & Dragons, you'll likely run across the Neogi in three forms - the Hatchling, the standard Neogi and the Master.  Let's break them down.

HATCHLING (tiny) - young and fledgling (AC 10-11; HP Level 1 Wizard), these are dangerous in large numbers and simple on their own.  Just don't wake up their older siblings.
NEOGI (small) - better natural armor (AC 15-16) and multi-attack makes this bugger a tougher beast to tango with, but this standard beastie comes with the main thing that makes these critters tick.  The Neogi has an Enslave ability (Short or Long Rest dependent) that pushes a Wisdom save.  Fail that, and you're charmed by the creature for one DAY (and it knocks out your Reactions - bummer).  Oh and did I mention that the Neogi talks to you telepathically during this whole thing out to a distance of one mile?  *shudder*
MASTER (medium) - not to be confused with the "Great Old" variety, these nasty variations on a theme get everything their small counterparts do (plus more than double their HP pool), and are freaking spellcasters!  Looks like these masters went all in for the Hadar fan club with a slice of Confused Bard, so be ready for some telepathic Vicious Mockery while being whalloped with Eldritch Blast for good measure.  Be careful too, they can function as a 7th-9th level caster, so that spell save may be meaner than you think at low level.  And I know I mentioned the "Hadar vibe", but any DM that does their research can mix up that power set to match another Elder Evil (wink-wink).

Now, each of these creatures has the Mental Fortitude of an Elf and Spider Climb, so watch your six.  What they lack in empathy, they make up for in numbers, and if they're following that Spartan Chuck-E-Cheese childhood, you can bet that what's coming for you ain't no pushover.

The Neogi are a Legacy Monster.
  Given their expansive and extensive lore dating back to second edition (2e), not to mention their pronounced influence within the Spelljammer history, their current iteration and inclusion feels lackluster.  There are dozens of fascinating creatures with deep history and ethos in Faerun and worlds beyond that are offered only a tiny passage in Volo's Guide, or Mordenkainen's Tome, or the Monster Manual talking about them, and, unfortunately, many of these passages end with a "nobody really knows" and a shrug (flips page).  
  To say that these are missed opportunities isn't exactly fair, either.  At its core, 5th Edition is intended to be accessible.  You don't want to bury the DM in mountains of back-logged history (some of it quite problematic today) just to get an interesting critter on the board.  So instead, I offer up my own approach:
This awesome monster can be a one-off.  A "well, that was weird, moving on" type moment.  OR, much like what happens when I do my research for each of these, this monster is a launching point of inspiration.  Truthfully, I hadn't yet considered the Neogi's place in my homebrew setting, but you can BET I've got one mixing now.  The rabbit hole I jumped into has some really cool avenues to play with, and I can twist and turn and mutate them however I see fit.
These things have a huge spider motif going for them - could they be distantly connected to Lolth?  Maybe the Drow that serve her hate Neogi, because they believe their banners as an affront to their queen!  You don't know (shrugs and cackles in DM).  
  My point is that for every moment of disappointment found in a feature, creature, or spell, there can instead be a tiny mote of inspiration, leading you to a setting with greater depth, immersion, and personal craft.

Happy worldbuilding.
​-Adamus

Though the origins of the creature rarely differ, their intentions in Io are often less miserable.  They are also HEAVILY influenced by the plane that they exist in.  
  WoWs of the Feywild will be more innocent and mischievous - still deadly, mind you - but their souls of dead sprites and nymphs don't understand the weight of their actions.  It's tragic, really.  These playful spirits are drawing creatures into their sight to feel not so alone...which kills their new friends anyway.
  WoWs of the Shadowfell carry a sorrowful weight and an unending desire to consume the living.  These spirits are tormented by the wales of their own death that they seek rebirth by draining the life force from other beings.  This usually manifests in alternative versions of their Consume Life ability, wherein they don't kill the target.  Instead, they inhabit their body, siphoning the creature of each of its attributes until only a husk remains...and a Wight is born instead.
  The more I write on these creatures, the greater the permutations and variations that manifest across the planes.  I consider what is in the Monster Manual as fact for the Material Plane, but as any Horizon Walker knows...Planeshift is one helluva drug.

Be safe out there, and beware the lights that drift in the forest.
-Adamus

Will-O-Wisps can be found all over Dungeons & Dragons, but for 5th Edition, look no further than the classic Monster Manual.  

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Displacer Beasts were once the prized jailers and guards of the nobility that filled the upper ranks of the Unseelie Court.  After the Massacre At Harrowhome, however, their prized position grew scattered, and one too many instances of their allegiance being swayed fell dim upon the Dread Queen Mab.  In the Ruins of the Season, deep in the harrowed halls of the broken citadels of beasts and men, prides of Displacer Beasts roam and hunt.  
  But not all nobility has turned a blind eye to these creatures with a love for the kill.  Excellent trackers, a Displacer Beast may sometimes roam with hunters and assassins of a deadly order.  Creatures contracted to hunt their own, these "Skipjacks" utilize the Displacer Beast as a dangerous ally in their pursuit of their fellow Fey.

GM's Note: Since the first campaign I ran in this custom setting, there have been old tapestries, panoramas, ancient texts, and obscure references that player-characters have stumbled across.  Each lore drop would be a tiny morsel of a much larger picture; an eight-legged displacer beast with boney spurs around the jaw-line, multiple tendrils lifting from its back like a living mantle, and a crown of black and silver spines protruding from its head.  This regal creature was always set upon a high rock surrounded by hundreds of other beasts, each bowing to it as if it were their king.  
  The first time this image was presented, I remember my players vigorously writing it down.  At any point following this, any players to be present during this strange initial reveal would bring it up again if ever they fell into an encounter with a Displacer Pride, but little came of it.  
​  Will we see more?  Only my players can tell you...

Tread safely under the borealis of the Feywild.
-Adamus

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