Dota 2 is a video game that was released in 2013. It is a sequel to "Defense of the Ancients". Dota was originally a player-made map (also know as a mod) in "" that proved to be successful with over 5 million active players. When "Warcraft: Frozen Throne" game got old, it was hard to make the map. As a result, Valve Corporation, with the help of the original maker (known only as Icefrog) started to develop "Dota 2".