Ultimately, this system will use a version of the combat system: to successfully activate a power, the player must make a successful attack roll for his character, versus the Mental DV of his target. If this attack roll succeeds, the power takes effect. If it does not, nothing happens, though any Legend or Willpower spent to activate the power are still used.
The mental DV of a character is derived by adding Wits + Integrity + Legend and then divide this sum by two, rounding up. Epic Wits adds its automatic successes to this final total, in the same way that Epic Dexterity adds to normal DVs.
Eroding Mental DV
Mental DVs erode on a scene-long basis. A character may be the target of such an attack a number of times equal to his Legend +1 before it begins to erode the character's defenses. Each subsequent attack during the scene reduces the Mental DV by 1.
Bolstering Mental DV
By spending a point of Legend, a player may boost his character's Mental DV by his Legend rating, just as with normal DVs.