So, where's the Sun on the Moon?

[AkaeiNox]

Well there is no sun from the 13th's moon either.

There are stars though.

[Seraphor]

It's already been explained ingame that Hydalyn is the Goddess of Stasis. In order to keep Zodiark in check, she had to have the astral nature so the moon just happens to be barren, like the First, because her powers lack umbral energies to balance it out.

Quick Google search is not showing anything, but what is the lore cause of Umbral wind?

If the moon is/was housing Zodiark and a gigantic mother crystal equivalent of dark energy, it being the source of umbral weather could be interesting.

We getting our Astrals and Umbrals mixed up again guys?
Astral = Dark = Zodiark/Bahamut/13th
Umbral = Light = Hydaelyn/First

[dragoelete]

Astral Elemental Lore

Astral energy is the light-based polarity present in all six elements (see Chapter 4 of Essences & Permutations - A Treatise of the Six Elements). The opposite of Astral energy is Umbral energy. Astral energy can exist in all 6 elements, as demonstrated by the odd-numbered months of the Eorzean Calendar. Likewise, The Twelve associated with Astral energy are Halone (Ice), Thaliak (Water), Llymlaen (Wind), Byregot (Lightning), Azeyma (Fire), and Nophica (Earth). Astral energy is most heavily utilized by Disciples of Magic, such as the Thaumaturge.
pulled right off gamer escape

also umbral litterally takes from the latin word umbra which means shadow

[Rannie]

We getting our Astrals and Umbrals mixed up again guys?
Astral = Dark = Zodiark/Bahamut/13th
Umbral = Light = Hydaelyn/First

You are completely correct.

for those that don't remember.
All is said in Shadowbringers when Urianger explains Umbral and Astral to us in IL Mheg. Plus explained by the watcher in Endwalker when talking to him on what happened during the final days and with the loporrits when they're explaining the crystals and why nothing can really grow on the surface of the moon as well as why they need those giant Skittle crystals... All in rewatchable cutscenes from the Journal in the Inn room or, if you have it, as a furniture item in your room or house.

The rewatchable portions are with the Watcher and Urianger...

[Seraphor]

Astral Elemental Lore

Astral energy is the light-based polarity present in all six elements (see Chapter 4 of Essences & Permutations - A Treatise of the Six Elements). The opposite of Astral energy is Umbral energy. Astral energy can exist in all 6 elements, as demonstrated by the odd-numbered months of the Eorzean Calendar. Likewise, The Twelve associated with Astral energy are Halone (Ice), Thaliak (Water), Llymlaen (Wind), Byregot (Lightning), Azeyma (Fire), and Nophica (Earth). Astral energy is most heavily utilized by Disciples of Magic, such as the Thaumaturge.
pulled right off gamer escape

also umbral litterally takes from the latin word umbra which means shadow

Incorrect, as Rannie said, Urianger and The Watcher each retcon this "lore".

Umbral is not dark simply because it has real world connotations with 'shadow', nor is Astral light simply because of the real world meaning of 'star'.
These were misconceptions made by scholars on the Source, basically naming things on if something is literally 'bright' or 'dark'.

The revelation came from Black Rose, and the conundrum of how 'dark magic' could trigger a 'flood of light'. Black Rose was considered 'Umbral' and it halted the flow of aether.

Umbral is linked to stasis, and a stagnation of aether, which manifests as 'light' in huge quantities, because that aether isn't going anywhere, it's concentrated.
While Astral is linked to energy and entropy, and this aligned with more dark magic and the void, because that aether is going everywhere, and dissipating rapidly leaving nothing in it's place, and thus an absence of aether is a signature of Astral alignments.

Everything post Shadowbringers has supported this, for example Hydaelyn's EX totems being Umbral and Zodiark's Astral.

If this offends your intellect, consider the following:
Umbral: Light causes shadows, there is no shadow without a light source. A shadow is not simply the absence of light, it needs the light to cast it.
Astral: Stars are pure entropy, burning fuel and kicking that energy out into space until they starve and die a cold death.

[Cleretic]

It all stems from the fact that it's not actually how that twist works in Japanese. Synodic Scribe described it to me once and it's... honestly probably even more confusing than what we got and didn't exactly stay in my head because of it, which might be why they changed it, but it instead tries to go for the angle of the Scions realizing they were being overly prescriptive regarding what light and darkness could do.

[YianKutku]

Everything post Shadowbringers has supported this, for example Hydaelyn's EX totems being Umbral and Zodiark's Astral.

Now I'm curious if they ever patched the debuff descriptions for Astral/Umbral Effect in Eden 7 (Eden's Verse Iconoclasm). There, the dark-coloured effect is called Umbral Effect, and the light-coloured effect is called Astral Effect.

This caused me a few issues dealing with the mechanics.

[KageTokage]

I kind of wish they never even brought up that information when they aren't/can't utilize it consistently due to the Source's general understanding of the elemental alignments being unchanged.