Joanna was raised in far-off Ustalav by her traveling merchant parents. Her bulk and keen insight kept her out of trouble, but her looks brought her suspecion; her bright blonde hair, powerful frame, and warm smile were seen as signs of Aasimar blood. Normally this would be considered a good thing, but the insular townspeople of Lepidstadt balked at 'foreign' blood (both geographical and planar).
In her youth, she was assaulted by Wraiths and nearly slain; in fact, she technically was. However, as she passed, she saw a vision of Pharasma's servants binding her soul back into her body and releasing the negative energy that had severed the connection. She awoke alone in the field, weak but alive. She sought answers at the local church, but no diviner could determine the reason behind her vision. She dedicated her life then and there to service to Pharasma, so that one day she may know why she was saved.
The church of Pharasma saw great promise in her potent combo of brawn, insight, and force of personality. She was trained as a cleric so as to put her strongest characteristics to use.
Joanna thought she had found a place in the world, and would eventually find a place in the hearts of the townspeople; however, this was not meant to be. One of the nobles (who had bitterly mocked and humiliated her in her youth) openly proposed to marry her on the church steps. His intentions unclear (and actions out-of-the-blue), she flew into a rage, both physically and emotionally beating the man senseless. As she came to her senses, she knew the damage was done; by nightfall the townspeople would be crying for her head. Assualting a noble was /not/ done.
To save her, the church had her transferred out that evening, sending her Kaer Maga. In the rush, she never found out who exactly gave the order to send her there or why. The choice of transfer felt oddly specific, given her (very secret) wishes to visit the city herself. Yet none of her superiors could have known, or would have thought to send her there instead of somewhere closer and safer like Lastwall.
Joanna is excited nonetheless; though she leaves her mother behind, she now gets to study the city of her dreams, and its undead inhabitants, who fascinatingly are allowed to walk freely. She is obsessed with studying life, death, and undeath's role in the process.
Joanna is not a single-minded destroyer of undead; in fact, she mostly pities them. She sees their actions not as one rebellion, but of immaturity and unwillingness to accept change. She wishes to study the creatures, both sentient and non, to further understand the importance and role of Death.