Spell mastery increases the mana cost of temporary spell gems that are not of the creature’s class, as well as any spell gems equipped by a nether creature that isn’t of it’s original class
I see. So, old-Imp Necromancer is out for payback and has forced his old bug onto an unsuspecting class perk as part of some grudge? The fiend!
Hopefully it will get fixed soon. Spell Mastery seems like so much fun.
Thanks for the info!