Horrific Mutation

Target creature gains +3/+3, Reach and Deathtouch until end of turn. If Horrific Mutation was cast from your graveyard, regenerate that creature and until end of turn it also gains "Whenever a creature dies this turn, put a +1/+1 counter on this creature.".
Flashback - Sacrifice a creature, then put the top five cards of your library into your graveyard.
Wild evolution can sometimes take a horrific turn.