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 (Discard a card: Attach to target creature you control. Equip only as a sorcery. This card enters the battlefield unattached and stays on the battlefield if the creature leaves.).