The main part of crystals is it raises your score by 20 hence it's an essential part of the scoring system of the game.
1) You gain 1 crystal when reaching 30 power
2) When you conquer someone with 1 or more crystal(s), you gain all of their crystals. If you were part of an attack by multiple players on the same colony (assuming you win!) you will get a portion of the crystals, depending on how many units you sent in the attack.
3) Each crystal raises your score by 20.
4) Each crystal you hold gives 0.25 metal/oil(So, +1 for 4 crystals)and 0.04 workers (1 for each 25 crystals) per tick for everyone in your alliance.
5) Crystals give a special ring around your colony
6) If two people are attacking an unconquered colony with crystals, the player with the largest amount of units at the end will usually get the crystals and the smallest will get the conquer, depending on the amount of crystals and the difference in two players attacking forces. (Other factors also apply, such as unit exp and unit build)
7) You can also gain crystals from attacking garrisons and sometimes relics have crystals too, and when players that had crystals are deleted the leave a camp with there old crystal's on it.
You don't seem like you really understand the game, owner of this thread.
If you want more details, read the wiki http://wiki.battledawn.com/index.php?ti ... #Garrisons
Or if you want to know more about the basics of the game, feel free to fill an application on the "Adopt A Newb Center". It will help you pass the learning curve more easily of course.