[Spoilers] Is the Adventurer from XI...

[StealthPaladin]

Well, both worlds do in fact share Cavernous Maws / Atomos which connect to Abyssea / the Void.

Abyssea is de facto a reflection of Vana'diel
The Void is the 13th reflection of Etheirys

It is feasible that Abyssea is simply Vana'diel's name for the 13th.
ShB and EW - especially Amaurot, Elpis and Pandaemonium - have many many FFXI parallels as well.

[Vyrerus]

Well, both worlds do in fact share Cavernous Maws / Atomos which connect to Abyssea / the Void.

Abyssea is de facto a reflection of Vana'diel
The Void is the 13th reflection of Etheirys

It is feasible that Abyssea is simply Vana'diel's name for the 13th.
ShB and EW - especially Amaurot, Elpis and Pandaemonium - have many many FFXI parallels as well.

The Void in XIV isn't really like Abyssea at all. Not too mention, the first Cavernous Maws in XI connect to the Crystal War era via the Walk of Echoes, as well as other alternate timelines rather than alternate worlds.

It turns out at the end of the Abyssea arc, the reason Abyssea has a red sky, no teleport crags, and is overrun with monsters is due to Promathia winning against Selh'teus and Abyssea's alternate Adventurer. He consumed them, and became Shinryu, who then who then created or let the Caturae in to attempt to destroy all life on Abyssea. Which, by the time of the Abyssea expansions, has not yet come to pass, and by doing the Abyssea content, you eventually come to kill Shinryu, and remove the existential threat to Abyssea.

Though they've never expanded on it really, at least to my knowledge( I haven't been back to play through Voracious Resurgence yet), Abyssea is essentially Vana'diel with shattered Mothercrystals.

Meanwhile, the only mothercrystal in XIV is Venat made, and was eaten by our spaceship and Zenos.