Creatures from the Plateau of Leng, referenced in Manual of Silence, one of the books in Lowls' footlocker.
In Chapter 97, the party learned more information about them. They are far more powerful and intelligent than the lesser ghoul-kin that haunt the graveyards of the Material Plane. They maintain complex societies and colonize vast reaches of the undergrounds of whatever plane they are on. They are surprisingly erudite, to the extent that all Knowledge skills are class skills for all of them, and any Leng ghoul can cast any spell from any scroll as if it had it on its spell list, and automatically succeeds at the caster level check needed to cast it. They are also diseased with Leng Ghoul Fever. As a functionof their physiology, they must eat flesh, but they are not necessarily evil.
They are relatively common in the Dreamlands, where they are known to populate vast necropolises, such as Igguzqaiz.
First Reference: Chapter 90
Other Notable References: Chapter 97, Chapter 101