One for All

One for All is a limited time game mode in League of Legends. Players battle in a 5v5 match in Summoner's Rift map similar to classic mode with the only different being that all champions on each team are the same. This mode will be available from 11/22 to 12/2.

Also, One for All games can be created and played in the Custom section and the map choice in Custom game  is not limited to Summoner's Rift only.

Process
The process for selecting champion in One for All is called Vote Pick which is somewhat alike to Draft Pick. A random player from each team will be chosen as the team captain and will take turn banning 6 champions (3 from each team) that all players have in the first step of this mode. After banning 6 champions, each player will have a chance to vote with their team to decide which champion will be played by the whole team. Player may pick any champion in their team's pool of champions (owned and free). If all players or the majority pick (3 votes) the same champion then the whole team has to play as that champion. In the case that no champion won a clear majority, a random champion will be assigned from the pool of votes.

Note that sometimes there are champions that your team has but the other team don't. However, the captain can ban any champion that both team have and therefore you can ban a champion that is not in the champion's pool of the other team. Also note that ,  and Syndra have been disabled in this mode, but can be enabled in custom matches.