Dota/Dota 2 & League of Legends were all based of the WC3 custom map Defense of the Ancients. The original inspiration for that map was a 1998 Starcraft mod called Aeon of Strife.
Accordingly, Alterac Valley could be modded into it's own game.
From: .../wiki/League_of_Legends:
The game's developer Riot Games was co-founded by Brandon "Ryze" Beck and Marc "Tryndamere" Merrill, who were roommates while they attended the University of Southern California. They partnered with Steve "Guinsoo" Feak, the previous designer of the popular Warcraft III: The Frozen Throne custom map Defense of the Ancients, and Steve "Pendragon" Mescon, the administrator of the former official support base for the map, to develop League of Legends.[49]
The original inspiration for "DotA" was a 1998 mod for StarCraft created by community member Aeon64 called "Aeon of Strife".[50] After the release of Warcraft III: Reign of Chaos and its subsequent World Editor in 2002, DotA was created by another modder, Eul. He ported and expanded the "Aeon of Strife" mod to the new engine and named it "Defense of the Ancients". Guinsoo later made DotA Allstars by inserting his own mix of content to "DotA", greatly expanding the number of heroes, added recipes and items, and introduced various gameplay changes. Guinsoo then passed the mod to IceFrog after accepting a job at the newly formed Riot Games.[51]
The idea of a spiritual successor to Defense of the Ancients was that it would be its own stand-alone game with its own engine, rather than another mod of Warcraft III, began to materialize at the end of 2005. League of Legends was born "when a couple of very active DotA community members believed that the gameplay was so much fun and so innovative that it represented the spawning of a new genre and deserved to be its own professional game with significantly enhanced features and around-game services."[52]
Riot Games officially opened its office in September 2006, and, as of 2013, has over 1,000 people working on League of Legends.[53] According to Marc Merrill, when creating the various champions in the game, instead of leaving the champion creation to just a few people, they decided to open up the champion creation process to everyone in the company based upon a template where they could vote on which champions made it into the game.[citation needed]
League of Legends was first announced on October 7, 2008. It was in a closed beta from April 10, 2009 to October 22, 2009. It then transitioned to open beta until release.[54][55]
