Prince is an exclusively male class associated with destruction. Specifically, ‘destroying (aspect)’ or ‘destroying via (aspect)
The Mind aspect is, obviously, related to Mind, namely thoughts and decisions. It is also associated with logic and reasoning.
POWERS
So first of all, a Prince of Mind would be incredibly strategic and intelligent. He would be able to see the best way to do everything, and go through all the logic and reasoning in something in a flash. If the class definition of ‘destroying via (aspect)’ is correct, the Prince of Mind would at some point during the game use this intelligence for destruction. I imagine the Prince of Mind as an Artemis Fowl-esque (love my taste in books 
) character.
However, as Mind is intertwined with thoughts, which follows a natural progression to sanity, the Prince of Mind will likely be able to destroy the sanity of either himself or his teammates.
A Prince of Mind would also be able to rip thoughts and memories from people, leaving them unaware that they ever existed. This could mean that the Prince of Mind would be able to destroy any unflattering memories or views of him, which would also likely tie into his personality, in being able to do a variant of that even without his powers.
A Prince of Mind would be able to destroy people’s reasoning over all or a single topic. Basically, the most intensely awesome debater ever. He could make them completely illogical and kind of mentally screwed up. Unfortunately for anyone on the receiving end of his powers, unless he makes a special effort, you’ll be aware of what’s happening to you.
As with all Princes a thing to remember is that they don’t ‘reduce the level of (aspect)’ they DESTROY it. This means that unless your team has a Page of Mind who has got their powers, all this is irreversible.
TEAM INFLUENCE
Anything he wants to be. He could destroy any reasoning that makes his teammates think that not doing whatever he wants is a bad idea.
However if the Prince of Mind doesn’t use his powers to influence his position in the team he’ll still be a good candidate for leader because of his strategic mind and high intelligence. He would be the team strategist, who everyone defers to when planning a battle, or in fact just anything.
CHALLENGES
As with all Princes, the Prince of Mind has to remember that the effects of his powers are irreversible. This means being careful that the thoughts or memories he destroys won’t be needed later on. Also, not going crazy making everyone stupid and then feeling all bored and unstimulated as everyone walks around like mental zombies.
Overall, if the Prince of Mind is cautious and uses his powers for the good of the team, he would be a valuable addition. However, if he goes crazy with his powers he may end up hurting himself as much as others.
Again, sorry this took a while. I’ve been kinda busy 