Source: Bestiary 3, pg(s). 115
Festrogs or dog ghouls as they are also known are a rare sort of undead created by a massive releases of negative energy usually created by a planar leak or the destruction of an artifact. Their body is mutated by this release into a more lean, muscular, animalistic form which often tricks people into thinking they are unintelligent, a foolish and often fatal mistake.
Festrogs look like hideously mutated, animalistic corpses. They backs are crooked, bent like the back of a hunting cat. Their limbs are similarly mutated, designed to enhance the speed of the festrogs when they run four-legged like dog legs. This would be scary enough if these parts came from different animals but they did not, the back and legs of the festrog were clearly once human but have been warped to make the festrog a more efficient hunting machine. The whole of the festrog's body is wrapped in tight sinewy muscle that seems to be compressing and warping its skeletal structure. The festrog's skin matches the rest of it body in unpleasantness as it is covered in pustules and boils some as big as a fist. The final mutation is the jaw, festrogs have an over sized bottom jaws filled with shark-like teeth designed to rip and rend their prey.
Habitat and ecology
Festrogs tend to dwell near wherever they were spawned although like regular ghouls they also tend to favour graveyards for their lairs. They particularly like graveyards with mausoleums as it gives them somewhere to hide during the day. Festrogs hunt only at night and prefer open terrain where they can easily run down their prey with their incredible speed. Festrogs tend to gather in small tribe like groups often holding what little affiliations they can remember from their previous life.
Festrogs are normally created by powerful bursts of negative energy caused by planar leaks, artifacts or occasionally the abilities of incredibly powerful undead. When struck by this negative energy any creature is normally killed (there are exceptions see Variants below) and their body warped by the negative energy. When they rise again they are now festrogs and they generally retain only scattered memories of their former life and are now driven by an unceasing hunger to hunt and kill. This hunger can never be sated as anything a festrog consumes instantly rots within its undead stomach.
Anyone who hits a festrog risks ripping open one of its boils or pustules that spray the attacker with disease-infected pus. Whenever festrogs feed on flesh they regain some of any health they may have lost. Festrogs can drop to all fours to run at full pelt nearly doubling their normal speed and allowing them to sprint. When sprinting on all fours they can easily outpace almost all of their prey matching a horse for speed.
There have been several reported variants of the standard dog ghoul. It seems that the massive release of negative energy needed to create them can have unpredictable effects.
Menadoran Festrog: Encountered only in the Menador Mountains that separate Nidal from the rest of southern Avistan Menadoran festrogs are festrogs created from larger but more primitive forms of life, usually creatures like hill giants, ogres and trolls. They are similar in appearance to normal festrogs but lack their intelligence and hunting tactics. They also have been known to, when eating, break into a shark-like feeding frenzy that is almost impossible to stop.
Living Festrog: This variant of festrog is not completely killed by the burst of negative energy that transforms it. Sometimes the transformation can go unnoticed until suddenly they gain an unwholesome craving for flesh. Unlike undead festrogs these living festrogs actually gain sustenance from what they eat meaning they hunt even more frequently than their undead kin.
High Festrog: These festrogs actually maintain enough intelligence and memory of their former lives that they can still use the abilities they had before their transformation. They are far more powerful than their bestial festrog kin, becoming powerful undead in their own right. Thankfully they are exceedingly rare.
Beastkin Festrog: This variant is created from the bodies of animals rather than humans. They retain only their animal-level intelligence but gain the ability to walk like a biped. There have been reports of encounters with festrogs created from lions, wolves and worgs. One Pathfinder even reported facing a bestial barghest festrog leading a tribe of smaller goblin festrogs.
Vampire Festrog: This festrog variant feeds not on flesh but on blood instead. In most other respects they are normal festrogs. One interesting thing to note is that they change colour depending how much blood they have consumed with fully-sated festrogs being bright red while hungry festrogs appear the dark colour of a bruise. Some vampires, particularly nosferatu, use vampire festrogs like hunting hounds. Those festrogs that are allowed to feed on the vampire's blood over time gain some of its supernatural abilities.