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 known as a mod) in Warcraft: Frozen Throne that proved to be successful with over 5 million active players. When Warcraft: Frozen Throne got old, it was hard to continue game development. As a result, Valve Corporation, with the help of the original maker (IceFrog) started to develop Dota 2. We do not know the real name of IceFrog (which is an alias).[1] Blizzard sued Valve over the copyright of Dota and lost.