Dirtwraith

Folk tales call this thing an undead spirit born from rotten soil under a corpse, but a dirtwraith is a clump of pale yellow, roughly spherical pods bound together by a web of tough, fibrous cords, buried among the roots of a larger plant. The bones nearby show how well it hunts, not where it came from. It is a native of the Abyss, where it goes by the name pit-root fungus.

The fungus feels prey through tremors in the ground. Its fibrous strands let it squirm slowly through the earth when it must relocate. It fights by animating its host plant, which strikes once per round for 1d4 points of damage per Hit Die of the dirtwraith, so a 5 HD specimen deals 5d4.

The host is mindless, so charms and other mental magic do nothing to it. Most hosts are AC 6 and fall after taking damage equal to the fungus's hit points, but that only costs the dirtwraith its club: once it thinks it is alone, it creeps off to find another plant, typically after 2d6 turns. To kill it, dig up the pods, or stay perfectly still until it surfaces to move.

The fungus is immune to fire, blunt weapons and mind-affecting magic. Once unearthed, it can only defend itself with spores: each pod puffs out one cloud per day. A creature hit saves vs. poison or chokes, taking 1d6 points of damage each round over the next 2d4 rounds; even a successful save leaves it at -2 on attack rolls.

A wizard of the demigod's inner circle brought spores home from the Abyss by accident and scattered them through a small town, which soon sprouted dirtwraiths. His fellows took keen interest once they saw the fungus was both an efficient killer and intelligent.

Age sets a dirtwraith's Hit Dice. A fresh one is a single pod with 1 HD that can work only little bushes and vines. Well fed, it adds one pod a month, each granting another Hit Die and the power to animate bigger plants, up to a cap of 12 HD.

Demons of every kind treat the pods as a delicacy, but they are toxic to natives of the Prime Material Plane. Even a few mouthfuls require a save vs. poison to avoid falling into a feverish coma for 2d6 days. When the coma ends, the victim saves vs. poison again; failure means death, and the corpse becomes food for a fresh pod.