Years ago there lived the first avatar named Shang Chi . Rava gifted him with the four elements when he separated the sprits from the humans
During his time there lived a fire emperor named Kane who was the first fire lord . Kane wanted to rule all the nation of benders , but he knewn that only the avatar who has mastered all four elements can rule all four nation.
So he declared war against the three nation and the avatar. The war was so tough that many soldiers died during the war , even the avatar couldn't stop or find a solution to the war .
Shang Chi later came down to his last option to separate the four nation , he knewn that if the war is to come to an end the four nation must be separated until the next avatar comes to restore balance among them.
So he told Cain his servant to go and look for the next avatar if he can't survive the war , Cain then ran into the forest in search of the next avatar.
Shang Chi entered the avatar state and then separated the four nation and was strucked by lightning by one of Kane soldier.
Since the nation were separated Kane could no longer rule the four nation. Kane learned that another avatar would be borned so he sent his soldiers to get and kill the next avatar.