Wyste

Wystes (pronounced 'wist') resemble enormous worms, typically 25 feet long and 2 feet thick. Their see-through skin reveals twisted, throbbing strands of organs. There are no eyes or mouth, only a large sucking opening ringed by long cilia tipped with claws, which serve as senses, feeding tools and weapons alike. As far as anyone can tell they act purely on instinct and exist only to eat.

Fiercely territorial, a wyste lunges as far as 15 feet from its pool at anything approaching, whipping its clawed cilia with surprising speed. Others nearby join in, drawn by the thrashing, and a wyste that kills something drags the corpse off to eat later, if it can keep its fellows away from it.

It may also try to drown a man-sized or smaller victim, wrapping around it on a hit and pulling it under. The victim escapes with a Strength check at -2 to Strength, but then needs a proficiency check in swimming or direction sense to reach the surface or become lost in the slime and drown. A trapped victim may try again once per wound, after any checks against drowning under the normal rules.

The slime is deadly to swallow: any creature not native to the Farther Dark or warped by it must save vs. poison or perish within 1d4 rounds.

Wystes have never been seen far from pools of alien slime and may be relatives of aquatic worms or leeches, though nobody knows for sure. They seem not to need air in the slime, or can stay under a long time, and ripples just below the surface often betray them. They can crawl slowly on land but never stray far, so a pool of opaque blue slime from the Farther Dark is always close by.

Two subterranean alien organisms produce that slime. One is a glossy black bulb that hangs from cave walls and ceilings on thick, fibrous roots; the other is a doughy white lump the size of a dog that crawls across the stone and feeds on the bulbs. Every so often the lumps open a dark pore and release a stream of blue ooze, which collects in stagnant, faintly slippery pools. The organisms are harmless themselves, but the pools draw wystes, and wystes draw slime-stalkers and other strange hunters of the Farther Dark.

Slime-stalkers prey on wystes heavily, and any wyste encounter has a 10% chance of including at least one of them. If the alien influence of the Farther Dark is removed, the slime-producing organisms die and the wystes follow within about a month.