Monster of the Week: Shadow Mastiff

Shadow Packs

These black hounds of dark fur and roiling smoke hunt in packs in the deep alcoves of the Shadowfell.  Led by an alpha, a hungry pack will descend upon nearby prey with ferocity and savagery.  The alpha howls to strike the target with fear, while the pack flanks, then pounces.  Efficient killers, the gloom only enhances their coordinated strikes.

The Best Boi

Shadow Mastiffs are summoned into service as watchdogs, temple sentinels, and bodyguards.  Religious sects and cults of the Shadowfell will call them into being as sentries to their dark work.  This ritual of binding is known to only the most dedicated to the forbidden arts, but is not exclusive to evil individuals; it is just the most common practice.
  These punishers of heresy and apostate can see into the ethereal world, and such extraplanar senses make them invaluable allies to whomever employs their service.

By The Numbers

  Shadow Mastiffs are stealthy and perceptive, but they won't be making any knowledge or persuasion checks.  With decent hit points and a low AC, expect these suckers in packs.  Favoring the shadows, they gain resistance to physical damage while in dim light or darkness, and, of course, are packing darkvision, PLUS the ability to see into the ethereal plane (suck it, ghosts!).  Like many of its lupine brothers, this thing listens and sniffs well, but its real trick is the invisibility it earns when in the shadows.  Be fearful of the pack of mastiff in a dark room.
  But not all Mastiffs are created equal, and every pack needs a leader.  A Shadow Mastiff Alpha is beefier in hit points and intelligence, possessing a howl ability that frightens their prey.  Though Alphas are heard of, their statistics vary and wane depending on the region you're in.  They are generally tougher, but a targeted attack can fell one in a round or two, especially if you can trap them in direct sunlight.

Shadow Mastiffs in the Ionian Shadowfell

Through an overabundance of summoning rituals and long life, Shadow Mastiffs are less an extraplanar ally and more a living, growing breed in the Planes of Shadow.  Once the complex ritual is complete, a Shadow Mastiff can persist through eons, evolving and adapting to its surroundings, forever in its prime of youth and virility.  Old Mastiffs become Alphas, adopting unique properties based on their experiences.  A Mastiff roiled in pack fighting may develop a hardened hide, or teeth and claws that rend with added ferocity.  Some adopt the abilities of a Blink Dog dominated into their pack, or copies the stalking stealth of a Displacer Beast they felled.  These extra properties can be random, but no less frightening and dangerous.  How they multiply is still a mystery, as these pups are created genderless, but some scholars surmise that when certain conditions are met, a Mastiff will drift toward the gender of the matriarch, and summon her own progeny.  If the Mastiff remains this way, no one knows, or much cares.

As for me, I'm down for a shadow puppy.
​-Adamus