Board Thread:Pokemon Arena X - Future Discussion/@comment-5537612-20130907061452

Because Bosses is not the right spot to talk about this.

So, mega stones. My own idea about how they work is as a temporary form change. You can activate the mega stone by clicking it, transforming your pokemon, and boosting your stats plus changing your ability. It should not last too long, long enough to give the pokemon an edge in a fight, but not too long that it becomes unfair. After the mega evo expires, the stone has to recharge and the user is afflicted by a debuff for every stat.

(sora/mikes/mlg's idea) When you Megaevolve, you can stay evolved for as long as you want, but firing off attacks will decrease an energy bar. Once that bar is emptied, the mega evolution wears off.

(srg's mastaplan) You can't mega evolve immediately, but instead have to deal damage to pokemon first, which fills up a bar. After it has filled up, you can trigger megalution. After it wears off, there is a cooldown on the meter, preventing it from filling up for a duration. 