Wow a lot of stuff happened in this month's manga. I need to reread it for I did not notice several key events until the last few pages where a "hidden" thing I suddenly realized is a very important thing, almost a hidden macguffin.

Spoiler: Chapter 097
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It is Eren who is the person who is pretending to have injuries and PTSD induced amnesia for he has infiltrated Marley. And for some reason he is mailing a letter to his half brother.

Most likely everything is now in reverse situations. Just like the 4 Warriors were trying to capture the Founding Titan and the King Behind the Walls it is now Eren and possibly the Survey corps infiltrating Marley and doing ______WHAT_______?

Most likely something involving the Tybur family those Eladians who are honorary marleyian aristocrats and the Warhammer Titan.