The Avatar Trio [A Percy Jackson and Avatar: The Last Airbender Crossover]

This is a crossover of Percy Jackson and Avatar: The Last Airbender as said in the title. It is a story about Percy being taken to a strange world where the Greek gods still live but don't have demigods. So pretty much the mortal world but... different. This world is filled with lots of people who can bend a particular element. Either, Water, Earth, Fire, Air. Only the Avatar can control all four elements.
Long ago the four nations lived together in harmony. Then, everything changed when the Fire Nation attacked. Only the Avatar master of all four elements could stop them. But when the world needed him most he vanished. A hundred years passed. Two Water Tribe siblings, Katara and Sokka, discovered the new avatar, an Airbender named Aang. Although his air bending skills were great. He needed a lot to learn before he saved anyone. But they still believed Aang could save the world.
But little did they know... they were gonna be helped by the hero from another world. Well dimension. Because the other Avatar was the son of the Greek god Poseidon. Frozen in time. But he barely knew.
He was also accompanied by Leo son of Hephaestus. Percy's mother died from a Minotaur. He met Leo on the way of moving on. Then he met his father. He told him he was taking him and Leo to another world.
Percy accepted. Poseidon told them minor details and then... you'll find out.