Marvel fans were today treated to the arrival of Thanos on Earth in the Avengers: Infinity War trailer and they probably noticed that he looks a bit different than the last time he was seen on screen in the Marvel Cinematic Universe.
Thanos’ biggest appearance in the MCU to date was in Guardians of the Galaxy, where he had a single scene interacting with the villain Ronan. During that scene, Thanos wore blue and gold armor that was quite similar to his comic book look, including a shining helmet.
However, in the Avengers: Infinity War trailer, Thanos looks much more spartan. The armor is gone, including the shiny helmet. Instead, Thanos is showing his bare arms and the only hint of protecting is a sleeveless breastplate (well, that and the all-powerful Infinity Gauntlet).
Back in July during Comic-Con International: San Diego, Avengers: Infinity War co-director Joe Russo explained why Thanos dropped his armored shell to IGN.
"[Thanos] has a more casual approach in this film, and it's very philosophical for him," Russo explained. "It's part of his character definition. It's a spiritual journey for him to collect the Stones and one with which he doesn't need armor. Once he starts acquiring the Stones, he doesn't need armor in the same way he did when he was a warlord. It's a very symbolic costume."
Up until now, Thanos as attempted to achieve his goals through the use of other villains, such as Ronan in Guardians of the Galaxy or Loki in Marvel’s The Avengers. In the post-credits scene of Avengers: Age of Ultron, we see him finally become fed up with this approach and deciding to do it himself. It seems this moment, in which he takes up the Infinity Gauntlet, that Thanos stops waging a war and begins the “spiritual journey” Russo references.