The cross hits the priest first, causing a high pitched screech as it burns him like acid. The Shade also seems less than fond of it, and retreats slightly.
Then Scurros strikes the demonic priest with the staff. The priest collapses. He stirs slightly, but is far to weak to move.
Before your eyes, he begins to transform back into a human.. by the time the metamorphosis is over, he is dead.
“She'd become a governess. It was one of the few jobs a known lady could do. And she'd taken to it well. She'd sworn that if she did indeed ever find herself dancing on rooftops with chimney sweeps she'd beat herself to death with her own umbrella.”
― Hogfather