Original
Lord of the Dark Dimension: Dormammu can use Probability Control. Friendly characters ignore damage dealt by the Mystics Team ability.

Welcome to My Realm: When an opposing character within range is given a power action, after actions resolve you may roll a d6. On a result of 5-6, deal them 1 unavoidable damage. Dormammu's other powers can't be countered.

Empower a Minion: Once per game as a free action, choose another friendly character of 150 points or less. That character modifies their combat values by +1.

Errata
Lord of the Dark Dimension: Dormammu can use Probability Control. Friendly characters ignore damage dealt by the Mystics Team ability.

See the Colossal Stamina and Great Size entries for more information.

Dormammu only has Empower a Minion on certain clicks. What happens to the chosen character if Dormammu does not current have Empower a Minion showing?
The power is only in effect while Dormammu possesses it. If it goes away, the effect ends. If it comes back, it resumes.