Lucy, our virgin, innocent girl couldn't be dresses as anything else than a slutty, creepy nun.
The slutty nun has a lot of sins to pay for, so Billy (as Father William) is taking care of her.
With some cleansing candles, the power of the lord inserted directly into her chest, and a special board to make her repent, he sure is sucking her demons right out of her ass, as she prays with every bead of the rosary.