During damage calculation in your opponent's turn, if this card is being attacked: You can target the attacking monster; make that target's ATK 0 during damage calculation only (this is a Quick Effect). This effect can only be used once while this card is face-up on the field.
When summoning Kazejin by himself is a preferable alternative to summoning Gate Guardian, that should tell Konami that we need a retrained Gate Guardian (possibly as a Fusion monster, or one that banishes its components from the hand and/or deck to summon). Hell, we got retrains of several other ace monsters, so why not Mr. GG himself?
I took 4,400 damage for just one attack. WTF? Can someone explain?