Monster Manual 3 Excerpts
Lurking within the rotting flesh of a slain adventurer, a rot grub poses a deadly threat to those who venture into ancient crypts and abandoned dungeons. Some claim that they are Torog’s spawn and that these ever-hungry worms seek only to cause pain and death in Torog’s name. Orcs abandon dungeons that rot grubs infest, while gnolls capture rot grubs and use them to torment captives in bizarre rites to Yeenoghu.
Today's Monster Manual 3 featured creature—the rot grub—is a deadly parasite that feasts on both living and dead flesh. Its voracious appetite leads it to burrow into a living creature, gorging itself on its victim’s muscles and innards. A victim of rot grubs suffers wracking pain that ends only when a rot grub reaches and devours its victim’s heart.
Dungeoneering DC 17: A menace in underground regions for untold years, rot grubs are held in check by the same hunger that makes them a threat. The inhabitants of dungeons vigilantly guard against rot grub infestations, squashing them before they become a great threat. When an infestation rages out of control, the survivors flee elsewhere, while the grubs gorge themselves on those left behind. When food runs short, the grubs die out, and only a few hardy specimens survive to find a new hunting ground.
Rumors persist of vast Underdark caverns filled with undulating seas of rot grubs. Supposedly, the grubs in these living seas feed on the decaying flesh of a forgotten god.