If you still haven't seen Avengers: Infinity War yet, there will be a lot of SPOILERS below, so be sure to read on at your own risk. Coming into Avengers: Infinity War, one of the biggest mysteries was the location of the Soul Stone, which was the only Infinity Stone that had not been revealed yet in the MCU, and after it was revealed, that lead to a number of theories about Thanos (Josh Brolin). The most prevalent theory has now been debunked by directors Anthony Russo and Joe Russo, in a new interview. This is your last chance to avoid SPOILERS, so read on at your own risk.
Towards the end of Avengers: Infinity War, Thanos finally does obtain all six Infinity Stones, and with the snap of his fingers, eliminates half of the Earth's population, including several Marvel heroes, and then disappears. We see Thanos on a rather peaceful planet, with a small house and a garden and the young child version of Gamora. There has been wide speculation that the place Thanos actually goes to is inside the Soul Stone itself, since, in the comics, the Soul Stone does house its own dimension, but that theory was definitively shot down by Joe Russo, who simply said, "No, no," when asked if Thanos had gone into the Soul Stone itself. Here's what Anthony Russo had to say about the place he goes to.
"He's like a holy warrior. Once he puts his armor down in that movie he becomes like a holy warrior and this is his resting place for him. He says in the film he's just going to sit and watch the sunrise."
Still, the Russos would not actually define what this place is, with Anthony Russo describing it as "the new planet," with Joe Russo adding that, "It's his whatever place that he goes." Joe Russo adds that while Thanos is someone who "murders people" and while his plan to kill people is at "random," with "altruistic" elements of his plan, Thanos ultimately has "some screws loose" and has a "messianic complex" that he's dealing with. Here's what Anthony Russo had to say below.
"Look, if you look at Thanos throughout the movie, what's noble about the character is it's not about ego for him. He believes that creatures and beings are suffering because of this. So he believes the road for the right way to peace and balance is through eradicating half of all life. And he believes that will bring balance and new life and peacefulness and joy to people - and he dedicates himself to that mission. His choices are remarkably focused on that. He's not killing people he doesn't need to kill. He only kills people in furtherance of that goal."
Interestingly enough, the Russo brothers had early confirmed that Gamora was alive inside the Soul Stone and hinted that is where Thanos went at the end of the movie. But their statements are contradicting one another. They earlier stated this when asked if Gamora was living inside the soul stone.
"She in fact is, yes. It was an attempt on our part, because we don't like two dimensional roles or three dimensional villains every villain is a hero in their own story and as insane and psychotic and brutal and violent as Thanos is, he's a more complex villain if you go on a journey with him emotionally. He does care for things and it is complicated for him to execute his plan and it cost him something. He said at the end that it cost him everything and that it was the only thing he loved which was Gamora which is why we put him back with her at the end. I just want to reiterate with the audience that he does feel true emotion even though he is a monster."
The Russos don't add any more context about where Thanos went at the end of Avengers: Infinity War, or what will happen with the Mad Titan in Avengers 4, during their latest interview with Uproxx. There is still no update yet on when the first trailer for Avengers 4, which is slated for release on May 3, 2019. Until then, fans will have Ant-Man and the Wasp on July 6, and then Captain Marvel on March 8, 2019.