You Cannot Hide from Me (Duskmourn: House of Horror Commander 360) - Common Magic: The Gathering Card

(An ongoing scheme remains face up until it's abandoned.)
At the beginning of combat on your turn, up to one target creature gets +2/+2 and gains vigilance until end of turn. It can't be blocked this turn.
At the beginning of each opponent's end step, if that player has less than half their starting life total, abandon this scheme.