Avengers: Endgame could show the biggest missing scene from Avengers: Infinity War - and feature two key planets from Guardians of the Galaxy. Marvel has taken a secretive approach to Avengers: Endgame, with a drip-feed of information meaning that, even now, the plot is largely a mystery.

Avengers: Infinity War had a runtime of 2 hours 40 minutes - and yet the plot actually skipped a lot of key story beats. One of the most frustrating was the Battle of Xandar, when Thanos and his forces razed that planet in order to acquire the Power Stone. According to Thor, that had happened a week before the film. On the commentary track, co-writer Christopher Markus explained that Marvel felt they just didn't see the need to show it. "If Thanos went to Xandar to get the Stone, you know what happened," he observed. "There was a big battle and he got it."

Related: MCU Movies That Avengers: Endgame May Revisit Via Time Travel

However, could the Battle of Xandar simply have been saved for a later film? The recently-released Avengers: Endgame Special Look features a shot of Thanos' vessel, Sanctuary II, hovering ominously in front of a CG planet that is easy to identify as Xandar, home of the Nova Corps (via Reddit).

Sanctuary II MCU Avengers Endgame

Assuming Marvel haven't just inserted a stock CG planet into this scene in order to mislead, the new trailer seems to indicate that Xandar will return in Avengers: Endgame. There are, of course, multiple ways that could work. Firstly, it's possible that Thanos could simply return to Xandar after his snap, although this is the most unlikely; there's no conceivable reason for him to go back there after already decimating the planet and taking its Infinity Stone.

More enticingly, this could be a return to the Battle of Xandar, showing audiences what was missing in Avengers: Infinity War. The obvious way to do this would be via flashback, although as there's strong evidence Avengers: Endgame involves time travel, this past event could be visited by Earth's Mightiest Heroes on their mission. Either way, it would mean viewers may get to see the fall of Xandar after all. It would also add an extra layer to Markus' comments; it's not that there's nothing enlightening there, it 's that it could be a big spoiler.

The fate of Xandar could well prove to be an important part of the MCU's lore going forward, given Kevin Feige has suggested the superhero Nova has "immediate potential" to appear in the MCU. In the comics, human Richard Rider became a member of the Nova Corps after their numbers were decimated by war, so the Battle of Xandar could serve as important backstory for a new and popular character. As such, it would be far better to actually see that on-screen.

Related: Avengers: Endgame Special Look Trailer Breakdown: 34 Story Reveals & Secrets

This isn't the only Guardians of the Galaxy planet revisited in the lastest Avengers: Endgame trailer, however.

Although the editing suggests it's Earth, the planet that the Benatar is flying away from in the above shot is actually Morag, the desolate and inhospitable world where the Power Stone had been hidden for millennia, concealed within a temple that was only accessible when the waters receded every 300 years.

It's unclear why the Avengers - who use the Guardians' ship after Tony Stark and Nebula returns to Earth - would go to Morag. If they're back in time, it could be to get the Power Stone itself, although we could also see Avengers: Endgame finally make use of that intriguing temple mural.

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