After winning the final Gods League (Totemius League), the player is moved to a King of Kings League, the winner of which receives the title King of Kings.
Receiving this title is the greatest honour in the game: there is only one King of Kings League for all players in the world and its winner officially becomes the best King of Thieves player!
Along with the title, the player also receives a royal throne, outfit and a crown. These throne and costume are unique and cannot be crafted or gained from Style-o-Thief machine. They are granted to the winner of King of Kings League and stay with the winner till the end of the next round. After that, if the player loses the top position, the royal throne is given to a new winner and the former King loses the ability to use it. If the player manages to stay on top, they continues sitting on the royal throne, which, by the way, not only looks awesome but has the highest stats as well.
But even if you lose a King of Kings league, you will be able to wear the Royal Robe. Just like any other outfit and throne, the royal throne, costume and the crown are shown during attacks, replays and dungeon saving (so you always know when you are being robbed by the King), and the name of the current King of Kings can be found on the leagues' leaderboards and in the outfit menu.