Larva

Larvae, evil dead from other planes who led especially selfish lives, are now doomed to spend their wretched existences serving evil on the Lower Planes. Larvae are horrifying 5-foot-long worms, sickly yellow and covered with viscous, foul-smelling fluid. Instead of a worm's head, they have distorted faces resembling the mortals they were in life.

Larvae communicate with one another through instinctive body movements that cannot be interpreted by others.

Larvae have no will of their own and simply lie in giant, quivering masses on the grounds of the Gray Waste. However, when commanded by a greater power - that is, just about anything in the Waste - larva will attack en masse.

Those bitten by a larva often contract a rotting disease. Those contracting the disease develop a painful skin rot, which is typically fatal within a month.

Night hags herd larvae to use them as bargaining chips in the Gray Waste. Lower planar powers use the larvae to form quasits and imps, and in return they agree not to enter night hag territories. Larvae are the sole means for creating imps and quasits.

Powerful liches feed on larval energies to maintain their undead immortality, and in return the liches destroy creatures who refuse to trade with the hags. The complex bartering system is sustained by the growing numbers of lower planar inhabitants.

Because imps and quasits later advance to become greater fiends, larvae are the foundation of the population of the Lower Planes. Because all larvae are equally lowly, fiends select them randomly to transform into other types of creatures as needed. How the larvae become higher creatures depends on the fiends that transform them. The baatezu, for example, cast the larvae into pools of flame, where the larvae suffer for 11 days before emerging as cruel new creatures. Other fiends have different ways to promote larvae.

Note: Larvae originally appeared in this form in the Planescape Monstrous Compendium Appendix I for the AD&D game from TSR. Their use here is for the purposes of providing context for the campaign only.