The 8th umbral calamity

[VigilanteXII]

And yes, there is a causal loop in the story, but that doesn't mean that the loop needs to be completed every time, because if it doesn't, the timeline would simply branch. So for example, in the 8UC timeline, the WoL never went to Elpis, and therefore the loop couldn't be completed, but that's fine, the timeline will simply branch off but will still share the same origin, because there's always going to be at least one timeline in which the WoL does go to Elpis and ensures the loop exists, and every other timeline can enjoy freedom from this obligation and do as they please! (At the cost of being branched off, of course)

I don’t think there was a causal loop involved. Believe Elidibus called it a “convergence of timelines”. The way I understood it, there’s basically two timelines, one where we went to Elpis and one where we didn’t. But since those timelines are almost identical, except for the memories of a few people, the timelines didn’t split, but kind of just collapsed into each other. That’s why Elidibus mentions that he both remembers us being there and us not being there, he has memories of both timelines, even though they conflict with each other.

It’s also why he’s very adamant that we don’t change anything, since doing so would cause a split and would most likely have left us stranded in that timeline (and would have left the original timeline short of one WoL). Admittedly we did a pretty bad job at that, but the memory wipe thing as well as Venat making sure to repeat history despite her new found knowledge made sure that our time there was ultimately of no consequence.

That is, until Pandemonium. Who knows where that is gonna lead.

[Iscah]

I don’t think there was a causal loop involved. Believe Elidibus called it a “convergence of timelines”.

I don't think Elidibus ever called it that, although Hydaelyn did - but then it could have simply been a poetic way of saying that the time loop is going to be completed soon.

It's worth noting that the description for the Argos mount highlights that we earned his trust prior to our first meeting with him on the moon "owing to the quirks of time travel", and of course Hydaelyn herself is also aware of those events already or she couldn't comment on it when we met her on the ship, indicating that we are already in the time-travel-affected timeline by the beginning of Endwalker.

So it cannot be that we change the timeline by travelling to Elpis. Those changes were already in place.

My own take on Elidibus's inconsistent memory is that it could be due to his fragmented memory being somewhat restored by receiving all of the Convocation's memory stones, which were partly produced by Emet and therefore just might contain his subconscious memory of meeting us in Elpis.