A Valve backed sequel to the very popular Warcraft 3 mod, Defense of the Ancients.
Confusingly, the official remake of the mod was called Heroes of Newerth and released earlier this year after a long Beta period. Heroes of Newerth and defense of the Ancients suffer from the incredibly steep learning curve and noob slamming. Our reviewer Squee reviewed Heroes of Newerth earlier this year and had a tough time as he was new to the game.
Valve are getting into the project to try and level the playing field with their player matching server skills.