League of Legends-1
Upon the World of Runeterra, war was a constant. Territorial disputes, greed and ancient rivalries drove the denizens of the world to wage one battle after another across the continent of Valoran. On this world, war has always been fought with magic in mass scale.
Armies would utilize magical runes or items to significantly buff their soldiers, sorcerers would weave massive fire storms that scorched the earth, mad alchemists would create magically driven chemical weapons, and great champions would rip the battlefield asunder in combat. For centuries, as sons continued the wars of their fathers, this tradition of magically driven war continued... until the abuse of rampant uncontrolled magic took its toll.
Though there were many Rune Wars before it, the last two Rune Wars forever changed the landscape and the creatures of Valoran. Once timid creatures transformed into ferocious beasts, the Jungle's fauna began to develop a taste for blood, and multiple new creatures and species began to pop into existence. Yet it was the violent earthquakes that nearly shattered all of Valoran that made it clear that another Rune War would doom the Planet.
With the fragility of Runeterra revealed to everyone, it was clear that something had to be done or all life on Runeterra would be extinguished. When they were needed the most, the greatest Summoners and Sorcerers on the content of Valoran created the Institute of War, and the League of Legends. The League was a collection of great heroes and villains, monsters and sorcerers alike, gathered to settle factional and territorial disputes of the aristocrats within arenas, rather than on battlefields.
Requiring Champions, the Summoners of Runeterra began summoning the greatest warriors they could find in alternate realities and worlds, as well as enlisting numerous of Runeterra's most unique warriors, scientists, mages and creatures that the world can produce.