Valve Software has announced plans to release Defense of the Ancients 2, a new game coming to the Mac and PC via Valve’s popular Steam service in 2011.

[ad#Google Adsense 300×250 in story]Defense of the Ancients (DotA) is a real-time strategy game with role-playing game elements that was originally developed as a “mod” to work with Blizzard Entertainment’s popular game Warcraft III. It remains popular to this day among Warcraft III players. The game pitted two teams against each other, each player controlling a hero character who purchases equipment and secures access to resources; the computer manages the actual act of creating armies to battle the enemy.

This time around, Valve is developing the sequel to operate as a standalone game using its flexible Source game engine – the same technology that powers releases like Portal, Half-Life 2 and most recently on the Mac, Left for Dead 2.

DotA will feature the original roster of more than 100 heroes, according to a preview posted by GameInformer.com. It will also utilize Steamworks, Valve’s social networking framework to manage game matchmaking and other aspects of community play.