pls say me how can i have a crystal

when you reach 20 power you "find" a crystal you will receive an event when this happens

the only other way to obtain crystals is to conquer colonies with crystals or conquer a garison

Note: if a player is conquerd by someone else and has a crystal you can attack him and steal his crystal if you win but you wont get the conquer you can also steal other players crystals when conquerd you just wont gain conquers