All For One is a game mode announced by Riot on November 22nd. It allows teams to all have the same champion, and have lot's of fun! The down side, Riot says this is limited. Here is a quote from their thread (http://na.leagueoflegends.com/en/news/game-updates/features/one-all-live): "One for All will be available from 11/22 to 12/2 so cover the battlefield with Cannon Barrage and have some fun!"