Sundering and specific character questions. [Spoilers]

[Vyrerus]

The thing that makes me question when the moon came into being are the buildings we see at Mare Lamentorum.

Perhaps Hydaelyn's summoners created it originally as a safe haven in case the Final Days returned and ended up completely destroying the world, but had it used as Zodiark's prison further down the line?

I think it's pretty much a research outpost turned memorial. If the Ancients were as invested in studying and stewarding the planet as Emet-selch says, then it makes sense that they'd want a full view of their planet. I actually kind of wonder if there was more than one moon before.

Of course, I can't help but think of our own moon's incidental function... it soaks up many many meteors, asteroids, and other celestial bodies that would otherwise touch down on Earth. Both small and large. Hence why it's covered in craters.

Perhaps the moon with Mare Lamentorum was made after the Final Days, but before Hydaelyn's creation. Perhaps as both a planetary observatory, and a meteor aegis.

[Iscah]

Of course, I can't help but think of our own moon's incidental function... it soaks up many many meteors, asteroids, and other celestial bodies that would otherwise touch down on Earth. Both small and large. Hence why it's covered in craters.

Yes and no. While it certainly has taken hits from meteors that otherwise might have hit Earth, the reason for the buildup of craters is that there is no weather or tectonic processes renewing the surface to erase them. The Moon's lack of atmosphere would also presumably mean no slowing effect or "burning up" of the descending meteor, so it gets hit harder and by bigger rocks.

It's only going to shield a very small fraction of the Earth at any one time – think about its size relative to the whole sky! – and I'm not sure exactly how much influence its gravity has but it's most likely just going to bend trajectories a bit, not "suck things in" and pull them off course.

[Vyrerus]

Yes and no. While it certainly has taken hits from meteors that otherwise might have hit Earth, the reason for the buildup of craters is that there is no weather or tectonic processes renewing the surface to erase them. The Moon's lack of atmosphere would also presumably mean no slowing effect or "burning up" of the descending meteor, so it gets hit harder and by bigger rocks.

It's only going to shield a very small fraction of the Earth at any one time – think about its size relative to the whole sky! – and I'm not sure exactly how much influence its gravity has but it's most likely just going to bend trajectories a bit, not "suck things in" and pull them off course.

I mean, there are also lunar meteorites from collisions with the right side of the moon. The low gravity and no atmosphere cause them to fall to earth, where they are only preserved in deserts, mostly the Sahara and Antarctica.

It does shield the Earth though, at least partially, and that is the direct reason for why it has craters. No meteorites hitting it = no craters. It's not just because its surface doesn't wear down, much. That's why we can still observe them, though.

In a magical world with a magical moon with a magical atmosphere created by magical people with magical creations being magical all the time, I'm sure they could magically have it perform better shielding than our mundane moon.

Anyway, it's something that's very fun to think about, especially when theories like this exist. Lunar Cataclysm

[Iscah]

It does shield the Earth though, at least partially, and that is the direct reason for why it has craters. No meteorites hitting it = no craters

That's not because it's "shielding the Earth" though; it's because both Earth and Moon are both objects in space that can potentially get hit by space rocks coming in from any direction. One wears all its scars forever on a rocky surface, the other hides them and wears them down or swallows them in the ocean without a mark to be seen.

Things might be aimed at the Earth but hit the Moon first. But just as possible they might come from the opposite direction and hit the larger Earth first.

Additionally, despite the "lunar cataclysm" description of the Late Heavy Bombardment theory you linked, as far as I can tell the only reason it's called "lunar" is because that's where the (debated) evidence for it is found. The article talks about it bombarding all four terrestrial planets and has a whole section on how Earth would have been impacted by it, with no mention of the idea of the Moon shielding it from anything.

Again, look at the size of the Moon in the night sky. That is how much of the Earth's surface it can shield at any given point, and the other half of the globe is completely unprotected.