Teto is the remaining god from the battle that took place to decide who should rule over the world. He is known as the God of games and after taking power he banned wars and placed regulations through 10 rules so conflicts could be dealt with games.
It was suggested by Sora and somewhat confirmed by Teto that he divided the world into 16 races, similar to one side of a set of chess pieces, in order to show that if one race beat all the others they would be permitted to challenge him for his status as God.
It was confirmed by Teto after stated by Sora that he dragged him and Shiro into his world due to the frustration of losing a chess game against ‘blank.’ He brought them so they could play against each other once more. This implies that Teto believes that Sora will most-likely conquer the world.
Teto was born from Riku’s dying wish to end the Great War.