Revelations from Fan Festival Around the World 2021

[Rosenstrauch]

That sentence is straight from Square Enix themselves.

On topic, I haven't finished a playthrough of FF4, but there were certainly a lot of callbacks to that entry. That game also had a blue tower on the moon, didn't it? What was it used for there (speculating in case its another intentional callback)?

Off the top of my head, so take this with a grain of salt...

The palace on the moon was a combination of several different functions. It served as a place to hold the Moon's Crystals—crystals in that game are essentially a repository of knowledge, history, and wisdom. It was also the resting place of the Lunarians, who entered a state of hibernation in the hopes of waking up to the day when humanity were their equals.

Furthermore, it was the entrance to the Lunar Subterrane, a massive underground cavern surrounding the Moon's core... basically, the Moon was actually a Moon-sized dyson sphere/spaceship, so to speak, and in that game's ending the Red Moon actually breaks away from the Blue Planet's orbit to travel into deep space for... uh, some reason. And finally, the Lunar Subterrane was also where Zemus was imprisoned in order to keep him from attacking the Blue Planet and trying to exterminate humanity.

[Vyrerus]

Off the top of my head, so take this with a grain of salt...

The palace on the moon was a combination of several different functions. It served as a place to hold the Moon's Crystals—crystals in that game are essentially a repository of knowledge, history, and wisdom. It was also the resting place of the Lunarians, who entered a state of hibernation in the hopes of waking up to the day when humanity were their equals.

Furthermore, it was the entrance to the Lunar Subterrane, a massive underground cavern surrounding the Moon's core... basically, the Moon was actually a Moon-sized dyson sphere/spaceship, so to speak, and in that game's ending the Red Moon actually breaks away from the Blue Planet's orbit to travel into deep space for... uh, some reason. And finally, the Lunar Subterrane was also where Zemus was imprisoned in order to keep him from attacking the Blue Planet and trying to exterminate humanity.

This is all correct. Few things I'll add.

The Crystal Palace/Lunar Lair/Mansion of the Moon People acts as a protective housing for the teleporter to the moon's core. The moon's core also houses sealed weapons that are exceptionally harmful to Lunarians, namely the Ragnarok, Holy Lance, Masamune, and Murasame. In the events of FFIV, Zemus has mind controlled exceptionally powerful monsters, such as Dark Bahamut and Lunar Leviathan(Ogopogo) to guard these weapons. He's also riddled it with monsters.

It's also connected via a dimensional elevator to the Tower of Bab-il on Earth, which can directly teleport anyone from the Earth to the Lunar Core. It's not explained so well in the game imo, but the Giant of Bab-il also resides in the Lunar Core, sealed alongside Zemus. The main reason Golbez needed the crystals of the earth was to open the dimensional elevator to teleport the giant down.

Seeing the Amaurotine memory/concept crystals in Mare Lamentorium's crystal palace type place feels like a perfect tie in/reference without departing from FFXIV's world. I love it already.

Edit: Oh yeah, the reason the Red Moon leaves is because FuSoYa decides that the Lunarians would rather not risk endangering humanity again, just in case.