Chertraum, Guide of Dreams

Flying
Betrayal — When Chertraum, Guide of Dreams
dies, if a spell or ability caused the spell or
ability's controller to lose life, discard cards, or sacrifice permanents this turn, return her to the battlefield transformed under her owner's control.
{2}{w}{b/r}, {t}, Sacrifice Chertraum: Prevent all
damage that would be dealt to target
creature this turn.