Rot Grub (Infestation, Vermin) CR 4
These diminutive vermin crawl off carrion and infest living hosts. They cause a fatal illness unless cured or killed. When first encountered, a DC 15 Perception check can be made to avoid them entirely. If this check is failed, the grubs have contacted and penetrated the victim’s skin. Once this occurs, the victim may make a DC 15 Perception check. If successful, he notices strange burrowing below the surface of his skin. Each round thereafter, a DC 17 Fortitude save must be made. If failed, the victim sustains 2d6 points of Constitution damage. At Constitution 0, the victim dies and the grubs seek a new host. During the first two rounds, the grubs can be killed by applying flame to them or by cutting open the affected skin, dealing 2d6 points of damage to the victim. If a DC 15 Heal check is successful, cutting damage can be reduced to 1d6. After the second round, only a remove disease spell can save the victim.
Rot Grub from the Tome of Horrors Complete, Copyright 2011, Necromancer Games, Inc., published and distributed by Frog God Games; Author Scott Greene and Clark Peterson, based on original material by Gary Gygax.