Larva

Larvae are the souls of especially selfish evil mortals, condemned to serve evil in the lower planes. Each is a 5-foot, sickly yellow worm slick with stinking slime, bearing a distorted copy of its living face in place of a head. They communicate only by instinctive squirming no one else can read.

Larvae have no will and lie in quivering heaps across the gray wasteland of despair until nearly any stronger being orders them to attack in a mass. Their bite deals 1d4+1 and bleeds 1 hp per round until bound, and the victim must save vs. poison or contract skin rot. After three weeks it costs 4 hp daily unless the sufferer lies completely still, and at one month it kills. Cure disease ends it.

Night hags herd larvae as trade goods. Fiendish powers turn them into imps and quasits and in return stay out of hag lands; powerful liches feed on their energy to stay undead and in exchange slay anyone who will not deal with the hags. The swelling population of the lower planes keeps the barter going.

One planar traveler, crossing the wasteland disguised with her party as a lich and its court, saw thousands of larvae driven across a slime-covered plain by fire-spitting mephits serving three night hags astride nightmares. Offered part of the herd, she was shown a brand to prove ownership, asked to watch a branding, quietly picked up a cold iron and escaped by cubic gate. The iron is now a prized curiosity in a wizard's castle.

Baatezu whisper of a coming ritual at the fortress of the ninth layer of the hells, the Great Unbinding, by which the Infernal Eight hope to destroy the tanar'ri. It would be long and dangerous, release titanic magic, and require destroying the life energy of a million larvae. The rumor is unproven, but baatezu have been buying larvae from the hags unusually fast.

Every imp and quasit begins as a larva, and those later rise to greater fiends, so larvae are the base of the lower planes' population. Fiends choose them at random for transformation by their own methods; baatezu cast them into pools of fire for 11 days, from which they emerge as cruel new beings.