Source: Pathfinder Bestiary, pg(s). 146
Ghouls are undead that haunt graveyards and eat corpses. Legends hold that the first ghouls were either cannibalistic humans whose unnatural hunger dragged them back from death or humans who in life fed on the rotting remains of their kin and died (and were reborn) from the foul disease—the true source of these undead scavengers is unclear.
Ghouls are generally humanoid creatures, possessing long, sharp teeth, their pallid flesh stretched tightly over starved frames.
Ghouls lurk on the edges of civilization (in or near cemeteries or in city sewers) where they can find ample supplies of their favorite food. Though they prefer rotting bodies and often bury their victims for a while to improve their taste, they eat fresh kills if they are hungry enough. Though most surface ghouls live primitively, rumors speak of ghoul cities deep underground led by priests who worship ancient cruel gods or strange demon lords of hunger. These "civilized" ghouls are no less horrific in their eating habits, and in fact the concept of a well-laid ghoul banquet table is perhaps even more horrifying than the concept of taking a meal fresh from the coffin.
Ghasts are advanced ghouls, strong enough to paralyze even elves, who are normally immune to ghoul's paralysis abilities. Ghasts roam in packs of their own kind or lead groups of common ghouls. The stink of death and corruption surrounding these creatures is so overwhelming that it threatens to sicken any living creatures in close proximity.
These aquatic cousins of the ghoul lurk near hidden reefs or other places where ships are likely to meet their ends. Lacedons are generally as quick and agile in water as they are on land.