As promised, Blizzard has now opened the beta testing of Heroes of the Storm, their team brawler/MOBA starring a roster of Blizzard heroes. They offer new Super Sonya and Mad Martian Gazlowe Skins and also kick off a Heroes of the Storm Ultimate Fan Art Contest with DeviantArt to celebrate the news. Here's a new Enter the Nexus trailer and part of the description of the game:

LET THE BATTLE BEGIN!
Heroes of the Storm™ is a raucous online team brawler starring your favorite Blizzard characters. Build and customize heroes from across every Blizzard universe to suit your play style. Team up with your friends and engage in fast-paced mayhem across varied battlegrounds that impact strategy and change the way you play the game.

BLIZZARD HEROES IN A NEW LIGHT
Heroes represents more than 20 years of Blizzard gaming history, settings, and iconic characters, all mashed up into an epic, off-the-wall team brawler. Fight out classic showdowns such as Tyrael vs. Diablo and Arthas vs. Uther, or settle those late-night debates you’ve had about who’s the stronger leader—Raynor or Thrall? Could Zeratul take down Illidan in a fight? Who’s more badass . . . Kerrigan or the Demon Hunter from Diablo III? The combinations of Blizzard heroes and universes are endless.