Introduced in Tim Hitchcock’s module Hungry Are the Dead (along with several variants), festrogs are animalistic undead similar to ghouls—a good low-CR option that’s viscerally disturbing but avoids the risk of total party kill by paralysis. Because of their unique genesis, truly perceptive undead hunters might be able to track them by seeking out the violation that spawned them.
Girard of the Hounds is a young necromancer who specializes in canine undead. Festrogs are his favorite servants, easy to control yet still terrifying for their feeding habits and contagious pustules.
The warpriests of Karth breed festrogs in their concentration camps by killing prisoners of war with negative energy, then allowing the canine units to maul the dead. As the camps are always in occupied lands, the warpriests don’t bother to contain the undead, but instead release them wild to terrify the locals into keeping curfew.
The Trollpeaks are notorious for trolls, packs of mangy wolves, and the ceaseless sense of unease experienced by travelers there. Many a body that falls under this miasma rises as a festrog…and some of the bodies aren’t even dead when the change occurs.
—Hungry Are the Dead 30–31 & Pathfinder Bestiary 3 115