Environment any land or water
Organization solitary, pair, gang (3–5), or pack (6–11)
Treasure none

Festrogs are aberrant undead creatures spawned by the spontaneous death and mutation of corpses caused by the release of negative energy associated with planar bleeding, the destruction of potent artifacts, or even certain magical attacks by powerful undead. Sometimes called dog-ghouls for their ability to run on all fours, this name often causes opponents to misinterpret their abilities and grossly underestimate their intelligence.

Ecology

A festrog is a deformed ghoulish humanoid wrapped with tight bands of muscle, so powerful it appears to have warped and contorted the creature’s bone structure. The creature bears a human-like face with an elongated skull and a tremendous lower jaw filled with serrated shark-like teeth. Driven by unearthly hunger to consume living flesh (though it will eat carrion or long-dead corpses if it cannot find fresh meat), the festrog hunts constantly. Whatever it devours merely decomposes in its stomach, giving it a slightly gas-bloated appearance. Its tainted, corpselike flesh is disease-ridden and covered in hundreds of welted boils, some swollen to the size of a halfling’s fist.

The create undead spell can create festrogs as if they were ghasts. The caster must be able to cast contagion, have access to that spell in a scroll or other magic item, or work with another caster who has access to the spell; creating the festrog expends the prepared contagion spell, uses an appropriate spell slot, or a charge from the magical source. If the corpse to be animated died of necrotic boils (the disease that festrogs spread) the contagion spell is not necessary.