Motivation: Find a means to achieve a worthy death
The Bishop's most potentially devoted servant was once a mortal priestess of the Shining Path. To prove her devotion, she dared the Hidden Tabernacle and sought the Bishop himself to beg him to end her life personally. To date, she is the only mortal to enter the Tabernacle and return alive… so to speak. Impressed with her devotion, the Bishop granted her the Black Exaltation, placed her at his right hand, and he broke her heart. She hoped for death and instead received immortality.
She remains loyal to her master, but his “gift” rankles her, as does his decision to keep her close at hand within the Tabernacle. She schemes through her subordinate deathknights to provoke a war between the Bishop and some outside party such as the Realm or the Bull of the North. Perhaps then her master will send her into battle where she might find a worthy death.