This post on Steam announces that open beta testing of Marvel's Avengers is now underway, offering the chance to flex your superheroic muscles in the upcoming comic book and movie tie-in game. Here's a Beta Deep Dive Video with a look at what to expect. Word is: "Marvel’s Avengers BETA is an epic, third-person, action-adventure that combines an original, cinematic story with single-player and co-operative gameplay*. Assemble into a team of up to four players online, master extraordinary abilities, and defend the Earth from escalating threats." Here's more on the game from its Steam Listing:

Assemble your team of Earth’s Mightiest Heroes, embrace your powers, and live your Super Hero dreams.

Marvel’s Avengers is an epic, third-person, action-adventure game that combines an original, cinematic story with single-player and co-operative gameplay*. Assemble into a team of up to four players online, master extraordinary abilities, customize a growing roster of Heroes, and defend the Earth from escalating threats.

Marvel’s Avengers begins at A-Day, where Captain America, Iron Man, the Hulk, Black Widow, and Thor are unveiling a new, hi-tech Avengers Headquarters in San Francisco. The celebration turns deadly when a mysterious enemy causes a catastrophic accident which results in massive devastation. Blamed for the tragedy, the Avengers disband. Five years later, with all Super Heroes outlawed and the world in peril, a sprawling adventure ignites when a determined young woman named Kamala Khan sets out to reassemble and rebuild the Avengers to stop the unchecked power of the secretive new force known as AIM.

Marvel’s Avengers continues the epic journey with new Heroes and new narrative delivered on an ongoing basis, for the definitive Avengers gaming experience.