I declare an attack with TKRO, my opponent try to destroy it, i chain Forbidden Lance. My question: Can my opponent play trap stun at that time then MST to destroy one of my back row, then he takes damage from a clear field and he Summon Gorz? Does it make sence?

Thank you.

If it's during the Damage Step, the opponent couldn't even activate Trap Stun nor Mystical Space Typhoon in the first place.

The only kinds of cards that can activate during the Damage Step are...

1.) Cards that specifically say they can somehow.
2.) Cards that directly affect the ATK and/or DEF of a monster(s).
3.) Cards that get ruled they can.


However, if it were outside the Damage Step, like during the Battle Step when you first declare the attack target (directly in this case), then yes, the opponent could use Trap Stun and Mystical Space Typhoon (assuming those are their only 2 cards on their field and they can be properly activated) and make their field empty by the time damage calculation is performed and the Battle Damage is inflicted to their Life Points (assuming nothing else is used that would prevent it, like a replay or something) and they would be able to Special Summon Gors by his effect.