Marvel Phase 3 is on full force now that Thanos has been cast! The rumors about Thanos have swirled even before his cameo in the first Avengers movie. He has already been confirmed and now the actor that will portray him has been finalized.

Being the ultimate villain at least until Phase 3, it was speculated that Thanos should be played by a prominent actor. One of the rumored names was Vin Diesel, who is playing Groot in the movie. Many were skeptical that an A-lister like Diesel would be confined to such a limited role. He himself has mentioned a forthcoming significant project and many believed that it would be Thanos.

Despite numerous denials and his insistence that Groot is his only character in "Guardians of the Galaxy" the rumors persisted. But we can finally put it to rest today.

From scoop site Latino Review, which has been quite on target the past few months:

"An article on James Gunn's post-production process reported a scene with Thanos on a rocket throne in Act 3, which suggests an appearance long enough that someone is going to have to voice the Mad Titan, someone that could take the part into Avengers 3 as a major villain. 

That meant Marvel was looking for an actor of some caliber, someone that could give a performance to a very complex, but very purple-skinned alien villain.

Our sources tell us that person is JOSH BROLIN!!"

Josh Brolin was last seen in the "Oldboy" Hollywood version alongside Elizabeth Olsen, who will play The Scarlet Witch in "Avengers: Age of Ultron." An actor of his caliber would add depth to the villainous Thanos.

Variety has since confirmed the rumor: "Josh Brolin has been tapped to play the villainous Thanos in Marvel's 'Guardians of the Galaxy,' sources confirm to Variety."

Recently, Variety also confirmed from director James Gunn that the Guardians of the Galaxy storyline will extend into the Avengers third installment: "We're definitely tied to 'Avengers 3."

Thanos will first appear in "Guardians of the Galaxy" on August 1, 2014 and spark the cosmic Marvel Phase 3 all the way to Avengers 3, where he will face off with Earth's Mightiest Heroes!