Monster Manual 5.5e
Tyrants among Corpses
Habitat: Swamp, Underdark, Urban; Treasure: Any
Ghasts are reeking, undying corpses closely related to ghouls. They hunger for the vices they enjoyed in life as much as they do for rotting flesh.
Ghast
Ghasts frequently organize ghouls into packs to despoil crypts and steal the wealth within.
Ghast Gravecaller
Ghast gravecallers wield fell magic and converse with corpses. They might pose as liches or vampires.