The Eternals? Marvel has always insisted that everything's connected, and quotes from the concept artists for Avengers: Infinity War suggest this vessel may a lot older than audiences first thought.
Sanctuary II was first seen in the post-credits of this was Thanos' ship, and that the Mad Titan had come to claim the Space Stone from Loki at last. Needless to say, Thor's belief that all would be well turned out to be very much ill-founded. The Sanctuary II returned in Infinity War, but if only for a brief time. And now there's new information on what went into its design.
Related: How The MCU's Titans Look Different From Thanos
The Art of Avengers: Infinity War book includes an entire section dedicated to the Sanctuary II, with Marvel concept artists explaining just how they designed it. Roberto Castro explains:
"Sanctuary II is Thanos' spaceship. So Charlie [Wood] and the Russos wanted to show Thanos' personality and power in the design. They wanted something between a sanctuary and a warship, so the challenge was to find that balance between both worlds - something aggressive but sophisticated. It's a huge flying fortress and a refined high-end flagship. Also, they did not want traditional technology for it. We stayed away from the traditional metal plating and tried to create a new surface for it. It looks like something made in ancient times, like a flying piece of jewelery."
https://imgur.com/a/K4oAGRG
In Castro's view, the vessel perfectly represents Thanos; it's carefully balanced, somehow both aggressive and defensive at the same time. He added that it looked like "something unique [and] almost like a handmade spaceship built centuries ago." Clearly the Sanctuary II's apparent age was a core part of its design, and that begs the question, did this ship originate from Thanos' homeworld of Titan"
After all, everything about a prequel film for the entire MCU, even showing how Titan was first colonized.
If Sanctuary II does indeed originate from Titan, then it's a hint as to the kind of philosophy and mentality that drove the Eternals. Particularly interesting is that sense of balance, which, in the comics, is typically associated with the Celestials - a race the Eternals worshiped. Thanos, of course, has inherited his own twisted and insane version of the idea, and uses it to justify his atrocities.
