I finally started working on a new power, but I'm not sure if it's balanced or not. What do you guys think?
Condemnation [-2]
Description: Your faith is so strong that you can temporarily call down the wrath of your faith, preventing your foe from bringing his full power to a fight.
Musts: You must have taken Righteousness in order to take this ability.
Skills Affected: Conviction.
Effects:
Condemn the Wicked. When facing an opponent, you may spend a fate point to perform a special Conviction maneuver that may temporarily suppress your opponent's access to a supernatural power. Roll your Conviction with a Difficulty (page 17) equal to the refresh cost of the power you wish to suppress. If the effort is equal to or greater than the modified refresh of the power, the target loses access to the power for one exchange, plus one additional exchange for each additional shift beyond the difficulty. If the effort is less than the refresh of the power, you instead take mental stress equal to the number of shifts needed to meet the difficulty of the roll.
For example, suppose your character is facing off against a Red Court Vampire. You wish to suppress the vampire's Inhuman Strength and roll your Conviction, obtaining an effort of +6. The difficulty of the roll was 2 (Inhuman Strength costs 2 refresh), so the vampire loses access to Inhuman Strength for 5 exchanges (1 + 4 shifts over the difficulty).
Later on, your character is up against an Outsider and he wishes to suppress the Outsider's Physical Immunity. The Catch for the Outsider's Physical Immunity is True Magic and it provides a +2 discount to the power cost, making the modified refresh cost of the power 6. Unfortunately, your character rolls poorly and only gets an effort of 4, meaning your character does not suppress the power and instead takes a 2 stress hit to his mental health track.