Private, Master Assassin

Deathtouch, Hexproof, Protection from artifacts
When Private, Master Assassin enters the battlefield he may assassinate 1 player, removing them from the game. When Private, Master Assassin blocks an attacking creature, he deals extra damage equivalent to the health of the attacking player. If Private survives, his power and toughness are doubled. Private, Master Assassin cannot be exiled, removed from play or put into the graveyard by any spells.