Blizzard DOTA will feature characters from across all Blizzard games, including Diablo III's Witchdoctor, Starcraft II's Nova and Thrall from the Warcraft series. Characters will fall into four classes, Tank, Support, DPS (damage per second) and Seige.
The game has been built by Blizzard using the Starcraft II mod tools as an example of the robust custom games that can be made with the toolset.
Blizzard DOTA is based on the popular Warcraft III mod Defence of the Ancients. Valve is developing the official sequel DOTA 2 while the original Defence of the Ancients developers have created their own free-to-play game League of Legends.
Blizzard DOTA is "coming soon-ish" according to Blizzard, with beta testing in the coming months.
The Starcraft II mod tools will be available "at or around" the release of Starcraft II: Heart of the Swarm.
Watch the first trailer for Blizzard DOTA below: