The Castle Perilous series revolves around Castle Perilous (the name is drawn from the Siege Perilous of Arthurian fable), whose lord is Incarnadine, a sorcerer. 144,000 doors (or "aspects") of the Castle each lead to other parallel universes. Some of these dimensions are magical, while others have little or no magic; one of the latter is Earth. Those who find themselves at the Castle often stay to become Guests, and (to their surprise) develop a magical power of their own. This gift is apparently random, and can range from a minor telekinesis limited to lifting pencils to super-enhanced senses to teleportation to full conjuration of matter.

• Gene Ferraro: main character, a philosophy major from Earth who gains the power of superb swordplay
• Snowclaw: a giant humanoid covered in white fur, who originally comes from a polar-like clime
• Linda Barclay: a woman from Earth who becomes a powerful sorceress
• Lord Incarnadine: sorcerer and lord of the castle
• Kwip: a lifelong thief who escaped execution by accidentally walking into the Castle through a doorway in his cell
• Cleve Dalton: a mild-mannered retiree
• Peter Thaxton: elder Englishman who is competitive in sports
• Osmirik: royal scribe and librarian of the Castle
• Sheila Jankowski: a young woman from Wilmerding, Pennsylvania who fell through an aspect of the Castle in her shower
• Jeremy Hochstader: a computer hacker
• M. DuQuesne: a French nobleman

• Castle Perilous (1988)
• Castle for Rent (1989)
• Castle Kidnapped (1989)
• Castle War! (1990)
• Castle Murders (1991)
• Castle Dreams (1992)
• Castle Spellbound (1992)
• Bride of the Castle (1994)
• The Pirates of Perilous (2015)

• Official bibliography of John DeChancie