Found on OMG! Ubuntu! site:

DotA 2, the standalone sequel to the popular Warcraft battle mod ‘Defense of the Ancients‘, is on its way to Linux.

In an FAQ listed on the official DotA 2 website the question of Linux support is addressed by Valve, the games maker:

“…Mac and Linux builds are currently in testing and will be available soon.”

The free-to-play MOBA game was released for Windows earlier this week.

While no firm date for a DotA2 release on Linux has been given some readers have been in touch to say that a ‘dota 2 test’ is showing up in their Steam library.
Posted here:
http://www.omgubuntu.co.uk/2013/07/dota-2-for-linux
Click the link for further links, images and a trailer of the game.