MSQ / Troia
I'm pretty sure y'all are overthinking Beatrice, or are at least on the wrong track.
She's a reference to Dante Alighieri's Divine Comedy. That's in conjunction with the Four Archfiends (Scarmiglione, Barbariccia, Cagnazzo, and Rubicante), Ciriatto, and Farfarello (all members of the Malebranche that guard Bolgia Five of the Eighth Circle of Hell). Seems they're going with Divine Comedy references this time around, or at least ones to the most famous Inferno part.
Went through Troia on Explorer mode; there's only one clear portrait in the one room, and it bears no resemblance to Beatrix I can make out.
The terms "eidolon" and "memoria" do bring IX to mind, but "eidolon" was used in XIII as well, and continuing the Divine Comedy reference "memoria" is just Italian for memory. The term "contramemoria" translates to "countermemory," just for the curious.

Originally Posted by
RyuDragnier
Let me paint the picture.
It's worth 357 gil.
As others have stated, Venat / Hydaelyn specifically ferried Minfilia and Emet-Selch's souls back from the First so they (or at least the latter) could play their parts in Endwalker.
There's a lot going on with Pandaemonium we still don't have answers to; saying Venat / Hydaelyn was hiding it down there the whole 12,500 years for no discernible purpose is jumping to a conclusion. We don't know who made the original memory stone that led us there, what's on the paired stone Claudien was chasing, why the Lahabrea we knew was so much more like Hephaistos than the austere man we met in Abyssos, what importance Erichthonios had to Athena's experiments, or why Pandaemonium's shown up in the Aetherial Sea in the present day. We don't know any of this. "Because Hydaelyn" is... a really hasty conclusion.
Also as stated by others, Zodiark was artificially stimulating the celestial aether currents to prevent the Final Days. We don't know what mechanism Hydaelyn used to sunder the planet beyond "that was her power," but if a world recombination was in the cards I'm pretty sure more would be hinting at it than some gatherer / crafter quests.
Just my opinion.
P.S. the 357 gil is just a reference to how much the new Scion portraits you can buy from an artist after completing the 6.2 Tataru quest with the Redbills resell for. It's not meant to suggest your opinion has low value.