Xyz Double Back (CBLZ-EN056) - Cosmo Blazer Unlimited

If you control no monsters and an Xyz Monster you control was destroyed this turn: Target 1 Xyz Monster in your Graveyard that was destroyed this turn and 1 other monster in your Graveyard whose ATK is less than or equal to the ATK of the destroyed monster; Special Summon those targets. Destroy them during the End Phase.