Tydus

Tydus is the arch-mage of Moonglow during the time of Ultima IX, whose power has given him delusions of grandeur.

Tydus had once been entrusted with the security of the floating library and the Oracle of Moonglow, but his power had made him greedy, and so he restricted access to the library. He even made a pact with dark forces, ordering a powerful daemon, Randolas, to guard his Heartstone. Also, when Duncan was searching for his dagger, he sent him on a wild goose chase to the dungeon Deceit.

When the Avatar wanted access to the library, he again used this tactic to first direct the Avatar to a cave full of thieves to get an imaginary staff of wisdom. After that failed, he directed the hero to the daemon who he hoped would kill the Avatar. However, the Avatar managed to make a deal with the daemon, resulting in him getting Tydus's Heartstone, and after some extortion finally got access to the library.

Trivia

 * Tydus's Heartstone purpose is left unexplained, and it is the only instance of such an artifact in the Ultima series.