Feast of Blood

Oracle Text

Cast this spell only if you control two or more Vampires.

Destroy target creature. You gain 4 life.

Card Rulings

10/1/2009 Whether you control two or more Vampires is checked only as you try to move Feast of Blood to the stack as the first step of casting it. It doesn’t matter whether you still control two or more Vampires as you finish casting Feast of Blood (in case you somehow sacrifice one to produce mana) or as Feast of Blood resolves.
10/1/2009 If the targeted creature is an illegal target by the time Feast of Blood resolves, the entire spell doesn’t resolve. You don’t gain life.