MIGHTY REVERT: DOCTOR STRANGE: When turning the dial, if this click is revealed due to damage taken from an opponent's attack, stop turning the dial. Give Doctor Strange a free action and replace him with a figure with the same name and less points that's the same number of clicks from its starting line. That character can't be given an action this turn and modifies its attack and damage values by +1 for the rest of the game. This power can't be ignored.

What happens if I don't have a figure to replace him?

Just don't give him the free action to replace him. You don't have to do that if you don't want to.

Even thought it says it cant be ignored?

Yes. You are never forced to give a character an action.