The Reaper

Trample, Deathtouch, Shroud
The Reaper enters the battlefield tapped.
At the beginning of each player's upkeep, if they don't control The Reaper, that player may sacrifice a creature. If they do, that player gains control of The Reaper. Whenever a player gains control of The Reaper, tap it, it doesn't untap during its controller next untap step.