Avatar TLA: The Spirit King [BOOK ONE]

The Supreme Overlord Momonga is transported to another world detached from his own, and finds himself in the presence of three children; Sokka, the warrior-in-training, Katara, a young waterbender, and finally Aang, the avatar of legend.

The four of them form a group of adventurers who travel across the world, helping Aang to master the four elements and defeat the Fire Lord. Momonga may be a heartless Undead, but the path he walks shall be of his own choosing. Whether that be good or evil relies on his own desires and those who influence him.

[Crossover between 'Avatar: The Last Airbender' and 'Overlord']