The Abbot

No creature in Barovia is older than the master of the Abbey of Saint Markovia in Krezk. This nameless holy figure, whom others call the Abbot, was drawn to the abbey after Saint Markovia died by Strahd's hand. He sought to restore the abbey after it fell to corruption, but was himself corrupted.
Angel in Disguise. The Abbot is a deva that has lived for millennia. He typically assumes the form of a strikingly handsome human priest in his late twenties or early thirties. More than a hundred years ago, the deva was sent from the Upper Planes to honor the legacy of Saint Markovia. He reopened the abbey and began tending to the physically and mentally ill. In so doing, he hoped to bring some much-needed light to Barovia. His efforts worked for a while, but then the Dark Powers began to corrupt him.
Imperfections. The Abbot's fall from grace started when the Belviews-a family of sickly, inbred leperscame to the abbey seeking salvation. The deva rid them of their diseases, an act for which they were eternally grateful, but could not cure them of certain human defects that had been present since birth. The Abbot became consumed with a prideful, obsessive desire to rid the poor Belviews of their lingering imperfections. The Belview family, however, bad strange ideas of what it meant to be perfect. They didn't want to be ordinary humans. They wanted the eyes of a cat, wings to fly like a bat, the strength of a mule, and the guile of a snake. In short, they craved bestial traits, and the Abbot, taking pity on them, yielded to their mad desires.
Ideal. "I want to rid Barovia of its sickness. By giving the devil his heart's desire, I bring salvation to him and his land." Bond. "I love the creatures I create, including my beautiful golems and mongrelfolk." Flaw. "I can't be corrupted. My heart is pure, my intentions noble and good."