Direct Dynamic Diamond Overhead!! (X-BT04/0042EN) (X-BT04)

You may only cast this card during your opponent's final phase if you did not take damage during this turn, and you have a "Prism Dragon" on your center.
[Cast Cost] [Pay 4 gauge]
[Counter] Deal damage to your opponent equal to 2 plus the number of times your opponent's cards attacked during this turn!! This card cannot be nullified, and its damage cannot be reduced. If your opponent's life would become 0 by this card, it cannot be changed by your opponent's cards. (Unrevivable)