Concept of other worlds

[Yuyuka3]

That does not explain how Thancred manages to get there too (as he's shown running with Reborn!Minfilia under Bizzaro!Limsa Lominsa Eulmore in the trailer after all, meaning he is definetely going to the First with us - the develiopment team confirmed long ago that Thancred, along with all the Archons except Krile do not have the Echo at all, so that's either a plot oversight or something else allows him to crossover....).

Hmmmm.....

I'd say our Echo is either the conductor for the travel, e.g. the tool with which we "throw wide open" the gate to the other dimension. Or, since Thancred is among those who got pulled there in spirit (wasn't he on of the, if not the, first?), it might be a manifestation of his soul or something? I don't know, I personally tend to the former tbh. Also, don't forget that last time we traveled to a shard (the 13th/World of Darkness), Nero also got there through the rift, so it's possible for someone without the ability to manipulate aether to travel to a shard if somebody else opens the way for them. We will have to wait and see on that, maybe we will get the answer as soon as tomorrow!