The Reaper

When The Reaper enters the battlefield, if you didn't cast it from your hand, you lose the game.
Haste, first strike, deathtouch
{u}: The Reaper gains hexproof until beginning of the next step or phase. Activate this ability only once each turn.
At the beginning of combat on each player's turn, that player may pay {3}. If he or she doesn't, creatures he or she controls can't attack
you that turn.