Could it be the kind of magic where you have a reservoir inside you that slowly replenishes based on your energy, that you can use to put into precious items (Gems or highly enchanted items) or use to power spells? Could the spells be that like code, rather than just "fireball." Like, a spell to create light would be start>light(200units)>Ball>2000seconds/oncommand>end, so each spell could be infinitely special/complicated? It'd also allow quite a bit of creativity- much more than just a "fireball" spell or a "candlelight" spell. Making a spell that's simply start>light>heat>ball>end, would be an infinitely-existing ball of unknown heat and light. It could be like a supernova for as long as the caster's energy sustains it. It would mean magicians are careful and thought out, at least in spells, with very good memory and reflexes.