@ZetsukoSo a brief overview of my magic: each mage has a specialization, one that usually broadens as they advance in skill. For example, Avad might have started as a lightning-only mage, then advanced from there. When casting a spell, one draws from a finite pool of energy that replenishes gradually over time and then speaks several words and draws a rune in the air, or more than one, depending on the power/focus, to direct the energy. More words can either equal more power, or more control. Both drain more energy.
The ability to use magic gives mages the ability to manipulate their energy, and thus they are able to store it, adding it to an object, almost entirely a prism. The reason it's usually a crystal is that the energy it takes to move power into an object is exponentially higher than the energy that is actually transferred, and crystals have the best ratio. The mage can then essentially use it as a battery of sorts. The stones, which have to be exceedingly high-quality to store six years' worth of energy, are then consumed, turning to dust.
That clear things up?
Also, I only killed the twenty-five standing next to the cart. I might not have made that clear enough. The thing about Avad is that his power is really front-loaded now that his stone is drained out. He uses his magic up, he can't do jack. So that burst of power is a one-time-per-battle thing, which, in a larger-scale fight, wouldn't make nearly as much of a difference.