Soul Binding Gate

To activate this card you must control no monsters, and a Set Spell/Trap(s) you control must have been destroyed by card effect this turn. During the Main Phase, if exactly 1 monster with less ATK than your LP is Summoned and you have "Z-ONE" in your GY: Destroy that monster, and if you do, take 400 damage, then inflict 400 damage to your opponent.