So he'd be a Grand Templar, and would only have Mage-Breaker and Arc-stone

EDIT: I've thought of a slightly different backstory for him. Basically, He fell in love with a mage and rebelled against the Empire a little while before the start of the RP, running away as a fugitive until he ended up in the Citadel. Naturally, he is a little kinder/less strict and has a slightly more sympathetic disposition. I don't know which story I prefer though.