PC Gamer - Valve’s main goal with Dota 2, says producer Erik Johnson, was “to build a sequel to a game that 20-odd million people around the world are playing”.
That’s Defence of the Ancients, a free player-made map for Warcraft III. It set out the template for a strange genre of game that’s since inspired a series of massive commercial releases. League of Legends alone has over 11 million active players, more than World of Warcraft.
Dota 2 sticks to the template closely: two teams of up to five players each pick a hero, and control it from a top-down perspective. But there’s already a war going on, between computer-controlled soldiers called creeps. Players are far more powerful, so creeps mainly provide easy kills to boost their experience and gold.