From a cinematic that Studio Mir and Riot created ahead of the Season 3 World Championship finals.

Features fifteen different players, all from different teams, being transported to an arena where each is empowered with abilities of a signature champion to fight for the Summoner's Cup. At the end, a still with finalists SK Telecom T1 and Royal Club, also empowered, is shown.

Official Reddit post (including official Riot reaction)