@Chameloshi: One of the things I did with powers was "take something considered OP as shit, and take it to the extreme in order to make it a bad thing." Magic immunity in Merc's case was a problem in a setting with magitech and magical medicine.

@kamimatsu: I think anything that reaches the threshold of OP is already a bad thing, and that definitely does sound so cheap right there.

Reminds me of how Brolandians are naturally shit at using magic (aside from Yoshkrydon DeLarso).