Nightworld — David Bischoff

By day it was paradise. By night it was a seething hell. Nightworld -- where for centures werewolves, dragons, griffins, and vampires served a computerized Prince of Darkness . . .
Where every sunset brought forth a call for the most heinous acts imaginable by the most frightening creature of all . . . Where a courageous young lord and a determined outworlder set forth on a journey of innumerable terrors to destroy the computer creature known as Satan in its own technologically horrifying haven of hell! "Wonderful! A journey in the company of ood travelers through a landscape of old menaces newly twisted -- a cleanly written adventure story." -- Roger Zelazny