Inertia Trap (Red)

“When this defends” is an event-based trigger. The power of the attack is checked at the time this resolves and becomes a defending card (i..e defends the attack). If the trigger condition is met only after this resolves, then this does not trigger.

If there is no attacking hero (e.g. this is defending against an ally attack), this does not create a token under the opponent’s control.