The world consists of the four main elements. Fire, Earth, Water, and Air.
With these four elements comes Life and Death.
These 6 things can be a power given to people through an accessory.
The accessory will grant powers to anyone but if used by someone who isn't suppose to posses its power can cause destruction and harm the user.
Once because one accessory fell into the wrong hands, people without any powers worked together to stop the element user. Since then everyone has worked together. Because everyone worked together there was no need for any more people to be chosen for the accessories power.
But over time people spread stories about the people who possessed the accessories making them something that majority of man kind feared.
With fear came tension, and with tension people started to fight, breaking the peace and brining back the need of the powers.