Ultima Underworld Clue Book

The Ultima Underworld Clue Book: Mysteries of the Abyss is 64 pages long. It originally retailed for USD$14.95 and was published in 1992. It was written by Aaron Allston, while in-universe Tyball, the villain, is the author.

Description
The book is actually narrated to a good part by the evil wizard Tyball in a letter to his former apprentice Malabelle. The narration is interesting in that it fills details on various NPCs, that in the game stayed unexplained, deepening how Tyball terrorized the inhabitants of the Abyss. It also contains a detailed backstory of the events between Tyball and Garamon that was not shown in the game, which led to the Slasher of Veils being brought to Britannia and Garamon's subsequent murder. It also holds explanations on Tyball's further motivations and reason for the kidnapping.

Further explanations are actually done by the Avatar, plus details on the game engine of Ultima Underworld are told without narration. The other content is described below. The book does contain many unique illustrations as well.

Book Content
The cluebook has the following content:
 * Tyball's tour through the Abyss
 * Advice to the traveller
 * Walkthrough
 * History of the Abyss
 * Engine details and tables

Trivia

 * This was the first hintbook to be assigned an ISBN code.