A half spirit, an existence that was almost absolutely impossible to exist, was rejected by his people from both his human side and spirit side after the first Avatar was born. Because the half spirit didn't belong to the spirit world, he could only live in the mortal world.
Eventually, he learned how to bend all the elements, and discovered that he was the son of an extremely powerful spirit making him immortal. He ended up becoming a traveler... Traveling across the world and learning several things about the world and himself.