This post from 2011 was one of a series on planar related stuff for the Weird Adventures setting. None of it saw publication other than on the blog..
Chronos hounds, or temporal hounds, are extradimensional beings who sometimes hunt the Prime Material Plane. Some ancient tomes hold that these creatures are benevolent, and defend causality and stability against horrors form outside spacetime. Observed behavior of chronos hounds is ambiguous at best, and those who may encounter them are urged to caution.
From a distance, a chronos hound has the silhouette of a large, lean dog. A closer look reveals that the body of the creature is actual more like a human's, perhaps specifically an androgynous youth's, twist and stretched to conform to a canine’s basic arrangement. It's front paws, for example, are slender, human-like hands. The heads of the hound is always blurred and indistinct, as if in constant motion, but there is the suggestion of toothy, canine jaws, and glowing eyes. Hounds appear to be able to speak by telepathy, but also make a garbled sound like the cough and growls of a pack of dogs, as if heard at the other end of long and empty hallway. Their skin is hairless, and the faintly luminescent blue-white of moonlight.
Only in the past decade, has metaphysics developed the proper theoretical framework to understand the chronos hounds--and even now those theories remain controversial. The most brilliant minds in the City hold the hounds to be a wave function which only observation causes to collapse into the form of the creatures described above. Thaumaturgic investigation suggests they serve an eikone called Father Time, or are perhaps extensions of his will. They act to prune "streams" of time and possibility--making reality from probability--toward some inscrutable purpose.
# Enc.: 1d6 (1d6)
Movement: 120’ (40’)
Armor Class: 4
Hit Dice: 4
Attacks: 1 (bite),
Damage: 1d6
Save: F4
Chronos hounds are only visible if they choose to be, prior to acting. Only some rare circumstance keeps a first attack from being by surprise. Their actions in this plane have a stuttering appearance, as if they are teleporting short distances rather than moving normally. Chronos hounds reduced to 0 hit points disappear entirely. Chronos hounds are able to pass through (or around) any physical barrier--or indeed temporal barrier. A combat with them may begin one day, only to have them break off the attack, and re-appear months or even years later. A first encounter with a chronos hound, maybe not be the true first encounter, from the perspective of the creature's timeline. Whatever subjective amount of time appears to pass in combat with them, 1d100 minutes have based for the world external to the combatants.
The greatest enemies of the chronos hounds are the achronal hyperbeasts, which they will fight to the death when they encounter them. Thankfully, these higher order dimensional monstrosities are seldom encountered on this plane.
5 hours ago