The future may be different, with electric lights and telegrams, but the world still needs the Avatar. The Avengers set in the world of Avatar: The Last Airbender. I really can't be more direct than that.

When Boba shows signs of a very old ability from his mother's side of the family, Jango puts out a call to his mother's homeworld to find him a teacher, and to recruit two new trainers to join the Cuy'val Dar. Hakoda assumes it will be an easy way to earn a few extra credits and help his tribe. He's very, very wrong.