Typically used with Self-Control.
In short: stay yourself. In this game, there exist not only hazards to one's body, but hazards to one's mind as well. Mind Control is a function of willpower and mental resolve. It can be used to focus on a difficult task amidst bothering conditions. It can also be used to subvert the attempts of those who would seek to trespass into your mind and soul and control your actions. If someone tries to brainwash you, tell them you are dry-clean only.
You must make a Mind Control check to avoid being commanded or manipulated into following someone's instructions. They make either a Leadership or a Negotiate check. If your result meets or exceeds theirs, you reject their request entirely. If your result is lowest, you see things their way and follow along.
If they make a Negotiate check, they can't suggest that you do anything that endangers you. They also can't suggest anything that goes against your Motivation, Alignment, or personal obligations and responsibilities.
If they make a Leadership check and the situation is dire, they can endanger you with their commands. You automatically succeed this check if your Disposition toward them is malign or worse (unless their request directly benefits your interests).
You must also make a Mind Control check when another character uses Perform to draw your attention. If you meet or exceed the other character's check, you remain alert. If your result is lowest, you gain the distracted condition while the performance is underway. If your Mind Control check is a Critical Failure, you gain the wide-eyed condition for the duration of the performance.
Many compulsory spells can be avoided with a Mind Control check, for instance Hear Thoughts and Sleep. In this case, you may add any points in Magic Defense to this roll. The mage makes a Casting Roll. You make a Mind Control check. If your result meets or exceeds the Casting Roll, you elude the effects of the spell.