The odd cutscene with Y'shtola and Runar in 5.3

[Iscah]

They were dead yeah but that didn't necessarily mean they didn't bring their bodies with them and then their bodies got sent back with Minfilia to stop the flood, but I don't think we really got a proper explanation on that.

It's a really big deal that the WoL was able to be brought across the rift with their physical body intact - not even the Ascians can do that. They just abandon their host and pick up a new one in the other shard when they arrive.

The Warriors are either possessing corpses like the Ascians do, or more likely are "solid aetherial ghosts" like the Scions in the First. They had to kill their original bodies exactly because they couldn't be transported across, and the souls needed to be freed to travel.

[BlitzAceRush]

It's a really big deal that the WoL was able to be brought across the rift with their physical body intact - not even the Ascians can do that. They just abandon their host and pick up a new one in the other shard when they arrive.

The Warriors are either possessing corpses like the Ascians do, or more likely are "solid aetherial ghosts" like the Scions in the First. They had to kill their original bodies exactly because they couldn't be transported across, and the souls needed to be freed to travel.

While the Ascians can't transport the living across, they can transport things, as some of their plans involved brining items to shards to get their plans rolling and Emet was using his "Solus" clone body, so either after having his grandson go through the trouble of using a facility to make him tones of spares (they dedicated a whole scene to those... wonder if they'll ever come up again...) he then had "another" facility made on the first just to make more so he could still be Solus there. Or, he can simply transport his empty meat puppet like we can anything in our inventory when we rift walk and then possesses it once he's at his destination.
Which would mean, as convoluted as it would be, if the Warrior's of Darkness reaaaaaaaly wanted to be in their own bodies on the source, they could be, even though they'd still be dead, though it's still most likely that they were just solid Aether ghosts, as they didn't leave anything behind when Hydaelyn and Minfilia pulled them into the rift for a chat.

[Iscah]

While the Ascians can't transport the living across, they can transport things, as some of their plans involved brining items to shards to get their plans rolling and Emet was using his "Solus" clone body

What "things" are you referring to?

Emet didn't bring the Solus clone body with him - he outright says he took over some unfortunate person in the First and transformed it back into another Solus lookalike. He just finds it convenient on the Source that the stock of clones means he can skip the transforming bit.

[BlitzAceRush]

What "things" are you referring to?

Emet didn't bring the Solus clone body with him - he outright says he took over some unfortunate person in the First and transformed it back into another Solus lookalike. He just finds it convenient on the Source that the stock of clones means he can skip the transforming bit.

Yeah, you're right, just re-watched the scene though I still think they could move their bodies around like they would items or objects, we can do it easy enough, though this calls into question our fight against Elidibus, he kind of throw our still very living selves half way when he puts us in the rift, perhaps it only works because we can already traverse it?
Honestly I don't think they did use their bodies, I just think it was possible but impractical and there wasn't really a reason.

[Rosenstrauch]

It's a really big deal that the WoL was able to be brought across the rift with their physical body intact - not even the Ascians can do that. They just abandon their host and pick up a new one in the other shard when they arrive.

The Warriors are either possessing corpses like the Ascians do, or more likely are "solid aetherial ghosts" like the Scions in the First. They had to kill their original bodies exactly because they couldn't be transported across, and the souls needed to be freed to travel.

Though all of this is true, I should note that this rule gets a little hazy when it comes to the Void. The portal used in the Crystal Tower raid questline allowed quite a few people to travel to the World of Darkness and back without having to abandon their bodies in the process. Shadowbringers also introduces the idea of "Hollows"—temporary holes torn into space that link directly to the Void. Taynor was sucked into one as a teen, only to reemerge well over a century later having apparently not aged at all. That same technique shows up again in the Void Quests introduced in patch 5.4, with the player's allies sending a Porxie (an enchanted clay doll, more or less) through to the other side. Gaia also demonstrates the power to create such portals during her brief stint as the Voidwalker (Eden 2 Boss), and this reappears as a mechanic against the Idol of Darkness (Eden 7 Boss).

The Ascians, of course, have no actual need to preserve their bodies since they can just seize new ones at their destination. But it does seem like sufficiently powerful casters can provide the means of traveling between worlds without shedding one's physical form, so long as they're willing to take the risks involved—such as portals necessarily working both ways, allowing voidsent the chance to cross over as well. That said, those risks are so high that it'd be unfeasible for most people, not to mention dangerous for folks other than the would-be world travelers.

[Theodric]

There's also the various crossover events where characters from other worlds such as Lightning and Noctis show up on the Source and then return to their home worlds. Ultimately, the writers will just come up with some reason to justify world travel as the story or rule of cool factor requires it. I'm pretty sure we'll eventually go world hopping again at some point, too. I don't think the First will be the only other world we visit during FFXIV's lifespan.

[BlitzAceRush]

Yeah, ultimately, it was a huge deal, now we can do it at will to the first with no downsides.
Spoilers to the ending of Eden

You even get a dialogue option to tell Gaia to pop in to the source herself, to which she thinks she likely could once she re-masters her powers.

So there're even laying foundation for that too.

[Erendis]

Though all of this is true, I should note that this rule gets a little hazy when it comes to the Void. The portal used in the Crystal Tower raid questline allowed quite a few people to travel to the World of Darkness and back without having to abandon their bodies in the process. Shadowbringers also introduces the idea of "Hollows"—temporary holes torn into space that link directly to the Void. Taynor was sucked into one as a teen, only to reemerge well over a century later having apparently not aged at all. That same technique shows up again in the Void Quests introduced in patch 5.4, with the player's allies sending a Porxie (an enchanted clay doll, more or less) through to the other side. Gaia also demonstrates the power to create such portals during her brief stint as the Voidwalker (Eden 2 Boss), and this reappears as a mechanic against the Idol of Darkness (Eden 7 Boss).

All those portals and holes are probably the same "Hollows". And who's to say Ascians were not involved in Hollow creation on the First? Especially since those mages bred specifically for that purpose...

[Dagget]

I think the odd background noise was intentional and pointing to something in the future. As well, Y'Shtola at the end cocked her head and winked at Runar while commenting "And there remain so many mysteries here that want for solving" which I think was a sly sexual innuendo at Runar.

[Raiya]

I didn't find anything odd about the scene. Interdimensional travel has been said to be impossible but obviously it's not, so figuring out how to do it is a challenge she's willing to tackle when there's spare time.

Just Y'shtola being Y'shtola.

Its not impossible just very impractical. Most means of traversing the rift before now have involved abandoning ones original body. The difference is the crystal tower. The amount of energy it stores is enough to allow one to breach the barrier, we already in ARR invaded the 13th aka the void with an alliance of adventurers. G'raha was able to pull us across to the first Physically after a number of failed attempts and we're able to traverse the rift to the first at will now because of both our canonically high aether reserves and because we got an aetheric lock onto Nordvrants aetherite network. Even the denizens of the first were able to open a gateway to the void thanks to a long project involving selective breeding and arranged marriages to produce mages strong enough to do so, though it wasnt until we got to the first that it was deemed a true sucess. Its pretty much not impossible to traverse the rift in the end but to do so it involves having skilled mages, exeptionally strong aether reserves and potentially involving specialised equipment like the Crystal Tower to be able to create strong enough gateways to traverse the rift. I could imagine that should the plot involve acessing the other remaining shards down the line that there is the plot tools and relevant lore in place to make it happen, we also got Ryne and Gaia currently chillin on the first and both are certainly to reappear in the story down the line.