the Four Nations have lived in harmony for many years, kept in balance under the watchful eye of the avatar, the physical manifestation of the world in human form. Upon the death of an avatar, he or she is reincarnated into the next nation in that cycle--Water, Earth, Fire, Air, and then back to the beginnings, much like a seasonal cycle of Winter (Water), Spring (Earth), Summer (Fire), and Autumn (Air). The Avatar has mastered the four elements thousands of times in his or her life, and will master them a thousand more.
Wars have started and ended, rebellions appeared and were crushed, kingdoms and empires rose and fell, and the avatar lived among them. Some Avatars have lived longer, harder, or more glorious lives than others. After all, even with the responsibility placed on their shoulders, they are still only human.
Even after her death, very few people forgot about the legacy of Avatar Zakura Ishiko of the Earth Kingdom, who was hailed as a mighty war hero responsible for restoring peace to the world at the young age of 23. The remainder of her life was long and prosperous, and while she did have quite the ego, her deeds did not become forgotten, and she was generally talked about in a good light. No one was flawless, after all.
Whatever the case, it was also a happy time for the world, with general peace all around. There were still pirates, ruffians, and miscreants crawling in the corners of the world, but those were folks who just never went away. Most importantly, the world was not at war anymore, thanks to Zakura's efforts, as well as the seeming rag-tag band of citizens that she gathered from around the world to put a stop to it. The efforts were international, but Zakura's gang had gone straight to the heart of the problem, cutting it off before it could spread further. With the war done, she spent much more of her life helping in reparation efforts, and getting the world back in balance. Her death was certainly mourned.
People were now looking again to the mighty Fire Nation for the heralding of the next Avatar. It had been just over 16 years since Zakura's passing, and that was the proper age for the next Avatar to be revealed by the spiritual leaders of that nation . This time, people awaited to hear from the mouths of the Fire Sages regarding the identity of the new avatar.
It was because of this that the life of a young man named Zeke changed forever. His name wasn't exactly known, either. his firebending skills were average for a boy of 16, and he had a few friends in the little island village he lived in.
As a result, it was somewhat of news to him when he received a summons to appear in the Fire Nation Capital City.
To cut a long story short, it was here that he was revealed to be the avatar. There was much pahtying, and benders and citizens from all four nations were at the event.
It also meant, however, that mastery of the elements became necessary. Zeke's uncle Enik obviously didn't want to throw his nephew right into the mess, but he understood the importance of cracking down to git 'r done.
* * * * *
Thus, a few days after then incident, after giving him some time to let it sink in, he approached Zeke about it.
"So." he nodded, the adventures of Avatar Zeke are about to begin. I'm sure you know of the cycle. For you it would be to master Fire, and then to learn Air, Water, and Earth. I am going to go under the assumption that you wish to learn more in the art of firebending before you travel the world... whatever the case, I'll be with you as I always have. Name your course of action, Avatar. We've got the world to see."