i think his CR in 3.5 is something like 22 but i thought it would be higher...i'll try to find his stats

edit : best i could find in five minutes

Kezef the Chaos Hound

Huge Outsider (Evil, Chaotic, Extraplanar)

Source(s): Champions of Ruin
Also Known As: Ravager of Heavens
Alignment: Chaotic Evil
Climate/Terrain: Any
Organization: Solitary
Rarity: Unique
Challenge Rating: 21

a putrid creature made of pure hatred which roams the outer Planes and eats the souls of the faithful before they can reunite with their gods. Thought to be created by the god Jergal to deny other gods the souls of their followers. It is a mastiff of rotted flesh, whose exposed black bones are covered with maggots.