Andariel, Maiden of Anguish

whenever Andariel, Maiden of Anguish is blocked during a damage step you may pay {1}{u}{b}. if you do, target one creature your opponent controls, that creature replaces Andariel, Maiden of Anguish in the damage step, if that creature were to die during the damage step untap Andariel, Maiden of Anguish.
"Andariel was the only female Evil. She aided the Lesser Evils for many years, but eventually she lost faith in their plots."-Deckard Cain