Neat concept, and mostly well implemented.
Down side was random charm system combined with losing 50% of them (plus those spent) when you lose. That means if you get a bad set of charms from 1 win, you're into a death spiral. It was many wins before I got ANY fire charms at all.
Not sure I like the "scared X mages" part as fighting them might help to power up for harder fights later on. Some sort of "store" system, where you can trade 2 charms for 1 you REALLY need, would help a ton.