Aatrox, The Darkin Blade

At the beginning of your combat phase, you may pay 3 life, choose one:
• Aatrox gets Double Strike until the end of this combat.
• Aatrox gets Lifelink until the end of this combat.
• Aatrox must be blocked this combat if able.

World Ender — If Aatrox deals letal damage to an opponent creature in combat, untap Aatrox, there is an additional combat phase after this one. This effect triggers only once for each opponent you attacked this turn.