so the crystal form is like megas?
My bad : look at 1ofthe4rocketbros’s answer 
They’re primal evolutions. The key difference being that the Crystal Pieces changing forms in battle doesn’t waste your Mega slot.
But I could use one per battle?
There isn’t a limit to how many Primal evolutions you can use per battle.
Only giratina and regigigas , and arceus are capable of using the crystal right?
Yes.
Yes I destroy everyone with my C. Giratina, C. Regigigas and C. Arceus like a noob
Really ? My bad, then… but if I may, isn’t it a bit broken considering they have one of the most powerful stats of the game !?!
Primal evolution was already broken to begin with. We had expectations that these Pokemon would be joining Mega Rayquaza from the moment they were conceived.
Ok, I understand !! Thks for the answer.