Pete took out a bunch of his old D&D books, here are some relevant quotes:
I’m paraphrasing, here, “He was winning the war in the Abyss against Orcus and Demogorgon when he was summoned by a mighty magic-user and pulled to the prime material plane. Cool. That fits right into the game we’re in.”
“Graz’zt is the handsomest of the demon rulers, at least by human standards. He appears as a huge, good-looking man, although his skin is shining black and his eyes are glowing green. Graz’zt is six fingered and six toed.”
The 3.0 Manual of the Planes is a nifty book. I especially like the 3-line descriptions of each plane:
“It is an infinity of clutching horror.
It is home to demons.
It is where morality crumbles and ethics perish.”