Rulings powered by The Netrep API. This card does not target. If your 'Elemental Hero' monster is in Defense Position, calculate damage as normal, using its DEF. If you activate 'Mirror Gate', Damage Calculation is resolved as part of the resolution of 'Mirror Gate's' effect. You cannot activate cards or effects that could usually be activated during the Damage Step. If the attacking monster or the attack target is removed from the field by an effect chained to 'Mirror Gate', 'Mirror Gate' resolves without effect.
Duelist Pack 6: Jaden Yuki 3
Activate only when your opponent's monster declares an attack targeting a face-up 'Elemental Hero' monster you control. Switch control of the opponent's attacking monster with the targeted monster you control, then calculate damage. Control of those monsters switches back during the End Phase of this turn.