I'd agree, normally, except we may run into shitstorms.
If I read his lore correctly, he's basically a science based character in an explicitly magical setting, which, while I am giving his player the benefit of the doubt, may result in lore kerfluffle to do with science and magic not mixing so well, akin to what happened with Kiri and John Doe back when Kevak still played properly and the other guy was around.
Again, Twin's call.
I still don't understand how John wasn't affected. Foxfire primarily targets the soul or energy, the burning or zapping is just a physical manifestation of a soul combusting.
Also with how John described his powers, he would need to be consciously aware of the entire universe 24/7 to not poof into nothingness. He was basically Mary Sue incarnate.
You made your fox capable of illusions... capable of shooting lasers. Turning a non-combat creature, into a combat creature, without a reason for why Kiri has murder powers.
Oh he's weak? He can shoot lasers. He can be countered? He can shoot lasers. He is weak to Kegare? He can shoot lasers.
Then you said he was weak because he's a glass cannon, yet he has runes that protect him from damage.
Oh and you said foxfire was more efficient than magic, which is bulls***, because you can't get more pure than purity itself.
Foxfire is akin to powdered alcohol (ratio may be different, but liquid is still the purest), while magic is liquid alcohol. And alcohol is magic.
Unless it's a different type of magic, in which case the comparison is invalid, because they must first have something to be compared on.
His power was simple, it didn't let him undo your magic, it simply made him immune.
Aka. he's the only one except the principal that can call actually beat you, without needing an OOC argument.
Though you would probably argue on the principal as well.