CLASS: Zombie mutation.
The first of these dim-witted scavengers is believed to have been an isolated mutation in which a normal zombie, in its constant cycle of decay and regeneration, probably absorbed the body of a small gastropod and created a new substrain of the zombie virus. Since then, the creatures have multiplied, transmitting the same mutation through their bite. Infected corpses will eventually lose the majority of bones and organs, their eyes and mouth growing to abnormal proportions as the flesh takes on an amorphous mud-like consistency.
An Escarghoul adopts the first hard, heavy object it encounters as a "shell", with a particular preference for flattened slabs of stone, which it hides behind when frightened. Though sluggish and dim-witted, it can withstand far more abuse than the average human zombie and its slithering body can traverse a wider range of terrain; even conquering the dreaded staircase. Its sticky skin holds fast to organic matter, fusing inseparably to prey at the lightest touch. It prefers to attack the stomach, biting through flesh and sucking out the entrails.