Saduj

Sadji is found in Ultima V, always sneaking around the roof of Castle Britannia in the night, acting suspiciously. He offers to join the Avatar on the quest, but this is deceit. In reality, Saduj is a spy sent by Lord Blackthorn to get possession of the Sandalwood Box, so that Lord British has no chance to escape dungeon Doom. Telling Saduj to password of the Oppression makes him tell the truth.

Because the Avatar revealed the truth with the obtained password, he/she left Saduj alone, so that he couldn't carry out his plans.

Trivia

 * Should the player let Saduj join anyway, he will betray the party in combat as soon as the Avatar has the Sandalwood Box. He will steal the Box and run away, and the game is lost.