So, this is just a concept for an alternate game mode that might be neat to try some time. The rules are pretty simple.
Each player starts as a Level 1 Mage. You cannot cast spells of a higher Level than you. Each time you or one of your cards destroys another card, and every time you or one of your cards do damage to a Creature equal to or greater than its Level, you gain 1 XP Counter. Every XP Counters grants you 1 Level until you reach Level 3, then every 2 further XP Counters grants you a Level until Level 5, and 3 XP Counters grants you a Level at that point for the rest of the game. There is no cap for Mage Level btw.
The only exception to the Casting Limit of your own Level is any Spell that is Class/School Specific. Those spells may be cast at any time, regardless of your level.
Your personal damage for your Mage is also adjusted based on your Level. At Level 1, you start with 1 Dice for Basic Attacks. If your Attack has more than 1 Dice, then at Level 2, you gain an additional Dice back, and at level 4, you gain a third Dice back. Mages with "Melee +1" or similar effects on their Mage Stats Card start with that bonus in addition to their normal 1 Dice. Starting at Level 7, and for every 3 Levels beyond, the Mage gains Melee +1, Ranged +1, and Channeling +1. Might add bonus Life to the effects gained, but I haven't decided yet.
Aside from this, the game proceeds as normal. This is something I've mostly been thinking about and part of it was even made up as I was typing this, since I hadn't fully detailed it. Thoughts and suggestions for improvements are welcome! Maybe it can be tested some time if anyone is interested.
Alternately, to slow the rate of XP gain, it could take 2 XP per level starting once you reach Level 2, rather than Level 3, or even from the start of the game. Personally, I think those first 3 Levels need to be quicker to allow for more decks to be viable though.
EDIT: Cards that target Minor creatures can be cast on a Level 1-2 Mage, but are immediately destroyed when the Mage reaches Level 3.