Mystell

Mystell is a resident of Killorn Keep on Atarka, responsible for the inner security.

When she met the Avatar for the first time in Ultima Underworld II, she tested him/her on knowledge and loyalty to the Guardian. Not knowing he/she was the Avatar, Mystell revealed she was the ears and eyes of the Guardian in the keep, trying to root out any traitors, voicing her suspicion against Altara.

But the Avatar, warned, didn't turn Altara over to Mystell, who in turn scolded him/her for killing Relk who had uncovered the ID of the Avatar (but had had no chance to tell it). Later she was found in the yellow zone of the Ethereal Void, dreaming of hoping to please the Guardian who sent her to this place every night to find the Shrine of Spirituality.

When the Avatar later returned to Atarka, it turned out that Mors Gotha had practically relieved her of her post, making her doubt herself if she had been loyal enough to the Guardian.

Trivia

 * The Avatar can tell her he is called Abraham Lincoln.
 * Also, if Avatar mentions being opponent of Guardian, Mystell merely thinks it's a joke.