Immortal Assassin

{t}: Until the end of your next turn, whenever a creature an opponent controls attacks, creatures you control get +1/+1 until your next end step. At the beginning of your next end step, exile Immortal Assassin.
At the beginning of your upkeep, you may discard a card. If you do, return Immortal Assassinfrom exile to the battlefield under your control.
"We're not done yet..."