契(けい)約(やく)武(ぶ)器(き)

As long as Pact Weapon is attached to a creature, you don't lose the game for having 0 or less life.

Whenever equipped creature attacks, draw a card and reveal it. The creature gets +X/+X until end of turn and you lose X life, where X is that card's mana value.

Equip—Discard a card.