Caverns of Socrates — Dennis L. McKiernan

They called themselves the Black Foxes, a group of adventure garners who transformed into: a pathfinder, a master healer, a bard whose music works surprising magic, a syldari Shadowmaster able to bend the darkness itself, and the leader, himself a warrior extraordinaire. They were chosen to help test Avery, an artificial intelligence designed to create a virtual reality universe so convincing that the Black Foxes would forget the outside world. But no one anticipated losing control of Avery. Now the only hope for the Black Foxes rests in carrying out a dangerous quest to defeat the Demonqueen and beat Avery at its own deadly game.