The Enemy Within (novel)

The Enemy Within is a 1994 fantasy horror novel by Christie Golden, set in the world of Ravenloft, and based on the Dungeons & Dragons game.

Plot summary
Sir Tristan Hiregaard periodically transforms into Malken, an evil beastly creature who controls a large criminal empire. Tristan is terrified by these transformations, and sets out to destroy his evil side.

Reviews

 * Review by Don D'Ammassa (1994) in Science Fiction Chronicle #172 (April & May 1994).