Corrupted Warrior

Betrayer 2 (When this card enters the Battlefield, pay 2 life, then, during the next End Step, search your Library for a Black creature card with converted Mana cost 2 or less and place it on the Battlefield tapped.)
During your Untap step, if you control 3 or more Black creatures, exile Corrupted Warrior, then return it to the Battlefield transformed under your Opponent's control.