In this week's episode of Obi-Wan Kenobi, Ben managed to infiltrate Fortress Inquisitorius and made a horrifying discovery. Deep beneath the surface, he found a number of Jedi and Force-sensitive beings who had been captured by the Sith Inquisitors and seemingly encased in an amber resin-like substance after being killed. The Jedi Master called it a "tomb," which was an apt description.
As you might expect, it's something that's generated a lot of speculation among fans (especially as the youngling we saw also appeared in the premiere's opening). Are they trophies or does Emperor Palpatine have some other sort of sinister plan for their frozen bodies? Heck, we don't even know if they're truly dead, hence why one theory, in particular, has sent fans into a frenzy on social media.
Many believe Mace Windu might be among those kept in Fortress Inquisitorius, with Obi-Wan simply failing to notice his old friend while attempting to rescue Princess Leia. It's certainly not outside the realm of possibility as Mace was a powerful Jedi and we never did learn what became of his body. We're not convinced, but there is a similarity, so who knows what might happen.
It's worth noting that Star Wars Rebels also featured a corpse frozen in a similar manner, with The Grand Inquisitor using Jedi Master Luminara Unduli's remains to lure Kanan Jarrus and Ezra Bridger into a trap. The big reveal there came when we learned the Empire was using her bones to attract Jedi. Perhaps keeping all those bodies on Nur is a way of bringing them directly to their fortress?
There's also a possibility all of this will tie into Palpatine's plans to clone himself, with the eventual creation of Supreme Leader Snoke the outcome. As always, we'll have to wait and see, but it would be pretty awesome to finally find out what became of Mace Windu after he took that fall...