A player in League of Legends takes on the role of a Summoner - a gifted spell caster who has the power to bring forth a champion to fight as their avatar in Valoran's Fields of Justice. With all major political decisions on Valoran now decided by the outcome of the contests that take place in the battle arenas, a Summoner is the key force of change on the continent.As the Summoner controls the champion in combat, the Summoner also influences the outcome of the match through the use of spells, masteries, and runes. Once a match is over, the Summoner gains experience and influence points. Experience points allow the Summoner to gain increased powers, while influence points allow the Summoner to gain access to new champions and power ups for use in future fights. Summoners may also spend influence points to change the aesthetics of the champions they summon.
Summoners are allowed the use of two Summoner spells during any fight in the Fields of Justice. These spells have a direct impact on the action in the battle arena. Summoners, for example, can heal their champion, damage opposing minions directly, teleport their champion anywhere in the Field of Justice they are in, fortify their team's turret defenses, and a slew of other game-impacting results. Summoner spells don't drain a champion's mana on use, but rather are usable again only after a short period of cooling down. As a Summoner gains experience and increases their power by fighting in multiple battle arenas, new Summoner spells will become available for use.
Before a battle arena match begins, a Summoner will make use of Runes to augment their champion's fighting abilities. There are four kinds of Runes a Summoner will use: glyphs (magical ability Runes), marks (offensive Runes), seals (defensive Runes), quintessence (powerful all-purpose Runes). Summoners are able to use a rune per level of power in League of Legends, and they keep their Runes in a tome called a Runebook. Before a match begins, a Summoner will be able to choose from three different rune configurations they have previously set in their Runebook. This allows the Summoner maximum flexibility in choosing a Runebook configuration best suited for whatever champion they might use in any of Valoran's Fields of Justice.
A summoner is able to focus their intense magical training into three specific categories - offense, defense, and utility - which collectively are known as masteries. Some of the more advanced masteries require not only a working knowledge of previous masteries within a single category, but also the knowledge of a specific mastery. As a summoner gains levels of power within the League, they are able to select which specific areas of interest to focus on. Summoner masteries are not set in stone; based on the type of champion you wish to control in a battle arena, masteries may be changed to better suit a summoner's needs.