This prologue is a narration by someone, like what they showed at the beginning of the Last Airbender series. Keep that in mind as you read this chapter.
Earth, Air, Fire, Water. These are the elements that shape our world, and for generations, it was the duty of the Avatar, the master of all four elements, to keep the peace between the Earth Kingdom, Water Tribes, Fire Nation, and Air Nomads. However, legends do tell of one particular Avatar who, instead of using his power to keep the peace, instead used it for his own personal gain, destroying any who stood in his way.
These actions did not go unnoticed, as the Avatar of this time was being watched by the four elemental dragon gods, the ones who ultimately created our world and gave us the power to control the elements. They, along with the spirit of light, had created the spirit of the Avatar as well, but they never intended it to be used for destruction. They realized that they needed another to keep the Avatar in check. And so, they each chose one warrior of their respective element, one whose sworn duty was to the protection of their people, and gave them a part of their own spirit, making these warriors the most powerful benders of their element. These four warriors, the Dragon Warriors, rose up against this wicked Avatar, and with their combined might, they struck him down. After the Avatar's defeat, the Dragon Warriors took it upon themselves to be the keepers of the peace should the Avatar fail to do so.
Seeing the promise that the Dragon Warriors would bring, the dragon gods themselves decided to have their spirit reincarnate, just as the Avatar's did, so that every time a new Avatar was created, a new group of Dragon Warriors would also rise. And when the Avatar did keep the peace, the Warriors would fight by his side. And where the Avatar was not, they would be. Now, with the Fire Nation attacking and the Avatar having not shown himself for almost 100 years, it may be time for the Dragon Warriors to rise up once again.