This is an interesting one. We don’t know *too* much about the Mind aspect yet, but I can make some guesses.
Thieves steal their Aspect to both affect the loser and gain something themselves. How do you steal Mind? Well, a Thief of Mind might be able to scramble, confuse, or even destroy opponents’ thoughts. They might start out as a naturally confusing or frustrating person and slowly hone their talents until it’s an actual superpower. They might also be able to wipe minds, stealing thoughts about a certain person or idea in order to keep their enemies from following through with a plan or remembering they caught the player doing something sneaky.
How would this benefit them? A Thief of Mind might be able to steal information from opponents and learn it themselves. Want to know a monster’s weak spot? Curious about gaps in Derse’s defenses? They’ll pull it out of something’s brain. They might also be able to enhance their own though processes/quickness, allowing them to calculate odds and come up with plans in record time.
Thieves tend to be morally questionable, though. As I said, they might be naturally bewildering. They might also pry or meddle with peoples’ minds without asking, which wouldn’t win them any friends. A Thief of Mind who wanted to cooperate with their teammates would have to learn boundaries. There are some lines that shouldn’t be crossed.