The news that Thanos was going to be one of the most signficant characters in Avengers: Infinity War shouldn't have come as too much of a surprise. After all, way back in February 2017 Kevin Feige confirmed that Thanos would be "the main character" of the movie and we now know we're going to get a fair bit of his backstory thanks to flashbacks.
But the linked reveal that Thor was going to be at the forefront of the movie was a little more surprising. Thanks to a variety of leaks and legitimate trailer details, we know that he's on a quest that will lead him to find Stormbreaker, the thunder-axe that will replace Mjolnir as his weapon of choice. But why would that be one of the most significant story threads in the film?
3. Thor's Journey
That journey will see him head to Nidavellir - the planet of the Dwarves - where, rumour has it, we'll meet Peter Dinklage's character and the axe will come into Thor's possession.
Logical thinking up to this point has centred on the idea that Thor will go to the planet specifically to get the Dwarves to make him the weapon, but the second trailer has thrown something of a spanner into the works thanks to one very telling sequence. And it's that sequence that might explain exactly why Thor's mission is counted as one of the most significant parts of the film despite it not having any real relevance to Thanos' conquest.
Think about it: Thor found out in Ragnarok that he doesn't need a weapon to act as a conduit for his powers - to borrow from Space Jam, the "special stuff" was already inside him - so why would he suddenly need a new weapon? If that was the real reason, it would be undoing the end of Ragnarok needlessly.
The reality may be different: the reality may be that Thor, Rocket and Groot go to Nidavellir for another reason and Thor comes into possession of the famed artifact Stormbreaker purely incidentally. And there's definitely evidence of that...