Nell shrugs, head shaking. "If you can reach them with that then you can use your blood to power some other spell instead. Even if you come up with some situation where mind control's the only type of spell that could save someone, it's so rare it's not worth what it'd cost to train for. That kind of magic takes practice just like any other. It's not like you can just do it out of the blue that once, you've got to spend hours sticking your fingers in other people's minds to learn it first."