Runeterra Legacy is an unofficial term for the canon that existed before the 2014 lore reboot. It could be considered an alternate depiction of Runeterra and The Main Universe, and potentially a part of the Multiverse.
City states on its depiction of Runeterra are mediated by the Institute of War, a powerful organization controlled by mages known as the Summoners. Champions from each city and area of Runeterra come to the institute to fight in the Fields of Justice for personal or faction goals.