Eren is alive and on Paradis, using a reincarnated Ymir to continue the rumbling.
Is it just me or has something changed among the Attack on Titan fandom in the last few months? I can't count how many posts I've seen claiming this series is "worse than Game of Thrones" or "has gone downhill since the start of the rumbling." Maybe these posts were mostly made by newer fans who joined during season 4 of the anime, or maybe they were made by die hard fans who've been reading since season 1. Either way, these folk have forgotten one key element of this manga: Every arc ends with a plot twist, each one bigger than the last.
I hate to sound like I'm gatekeeping, but anyone who believes Eren is dead after 137 haven't been paying attention. For one, this is the third time we've seen him "die." Also, you'd have to be psychotic to kill Eren without showing his pov!
Now of course, when you really break things down, there are only two options for Eren: he died in 137, or isn't in his Titan. Now, in a series known for major plot twists, which example seems more reasonable?
There are a variety of factors that lead me to believe Eren never left Paradis.
For one, the Founding Titan spawned from the feet up:
Seriously. Compare these two images.
Also, the Warhammer Titan used a remote cord in Marely that was attached to her left foot.
We have never seen a clear view of the Founding Titan's feet this arc.
Nope. Not once. There are many shots in which the upper 50% of his feet are seen, or the left foot is obscured by steam. But the feet of the Founding Titan are deliberately being obscured from frame.
Now for the second portion of the theory. The Rumbling seemed to stop in 137. Many have celled this a plot hole, as Ymir is clearly enabling the rumbling through her own free will. However, this seems far too convenient. I severely doubt the official theory of Zeke's death stopping the rumbling is true. Instead, I believe Ymir has been reincarnated as Historia and Eren's newborn daughter.
It's very clear that due to Zeke's death, the power of the Beast Titan will go to a newborn Eldian baby. Most fans agree on this. However, it seems many disagree with the power going to Historia's child, and Eren using this "titan of royal blood" to continue the rumbling.
I would agree. Eren using his own child to commit the extinction of the outside world is out of character. But It's far more likely that he's foreseen the ending of the series, and is continuing the rumbling through Ymir's wishes.
Of course, newborn Ymir would only have 13 years of life, but not if Eren ends the power of the titans after completing the rumbling! This would add far more meaning to the final panel of the series.
\"You are free\" From slavery, the curse of ymir, and the hate of the outside world.
Now let me make one thing clear: If Eren truly completes the rumbling, this ending will be FAR from happy or bittersweet. Billions of civilians have died cluelessly, along with all of the alliance. Eren will likely live in guilt and shame for all of his remaining years.
https://www.youtube.com/watch?v=OrQ0zZArUV8&t=3s
I highly recommend this video. It's an official music video made during season 3 of the anime that heavily foreshadows this theory.
Finally, Isayama has not lost his touch. I named my reddit account after this series! There's still a ridiculous amount of detail given to every panel! Please, give the ending of the series a chance. It just might surprise you.
TL:DR Eren is far from dead. Each arc of Attack on Titan ends on a plot twist. Eren is not in the Founding Titan, as evidenced from it spawning from the feet up, and the left foot being obscured from view in all panels, likely due to a warhammer cord. The rumbling ended because Ymir is reincarnated as Eren and Historia's child. Eren has her consent to continue the rumbling and kills all of the alliance. He lives in shame until the end of his days.