The Voker

Convoke, Invoke (Each creature you tap or sacrifice while paying for this card pays for {1} or one mana of that creature's color.)
Revoke {4} (When you cast this spell, any player may pay {4}. If any player does, counter this spell.)
Provoke
When The Voker enters the battlefield, you may sacrifice a tapped creature you control. If you do, return another target creature from your graveyard onto the battlefield.
Evoke {2}{b}