i wanna hear about the lore but the moon lore only
YEAHHHH ANON WANTS TO HEAR ABOUT THE MOONS!!!!
Okay so I'm going to keep this as tl;dr as possible because it would be VERY easy to go off on a tangent so I am sticking JUST to stuff where the moon or Moon Sisters are explicitly mentioned.
So according to Heart's Desire, vol. 3, there used to be three moons over Teyvat instead of one:
Aria - name is Italian for a single-performer vocal piece in an opera, but derives from the Latin for "air"
Sonnet - like the poem, but derives from an old proto-Romance word for "sound'
Canon - musical composition based around multi-voiced imitation; derives from Greek and Latin word for "law" or "rule."
(Make of these etymologies what you will.)
According to Moonlit Bamboo Forest(MBF), vol. 3 :
the Moon Sisters are older than Morax (more than 6,000 years old)
they're referred to as "daughters of prose and song"
they "ruled over the night sky," trading shifts in moving across the heavens in a silver carriage (think Helios in Greek myth with his chariot)
they were in love with "the stars of daybreak"/the "morning stars."
It should be noted that "morning star" is a term often associated with "dawn bringer," it may be associated with Phanes, the Primordial One (who is also known as Eosphorus/Phosphorus or Lucifer depending on which versions of Greek/Orphic/Latinized mythology you're looking at). Since MBF refers specifically to "the chambers of the morning stars," this may imply that the anthropomorphic "stars" are the Shades that Phanes made of itself.
Something caused the Moon Sisters to turn against one another, and the single remaining moon in Teyvat right now is the one remaining corpse out of three. (yikes.)
According to Records of Jueyun, vol. 4:
the three sisters were witness to a union between one of the Seelie and "a traveler from afar."
a great "calamity" fell 30 days later. (Whether the union is directly related to the calamity is EXTREMELY unclear, although some people [pooossibly myself included] theorize that the outlander who fell in love with the Seelie was the Second Who Came from beyond the firmament, who eventually challenged the Primordial One to the throne and lost. For more on this, see the Byakuyakoku Collection.)
For some miscellaneous flavor, here are some things associated with the moon/s that have caught my eye as I've played Genshin
Mondstadt literally translates to "Moon City" in German.
Liyue (璃月) makes use of the characters for "glass/colored glaze" and "moon."
Speaking of Liyue, the osmanthus flower is associated with the full moon and the Mid-Autumn festival. In Chinese legend, the first osmanthus plant is on the moon.
Glaze Lilies only grow at night.
There are WAY too many mentions of serpents consuming the moon and/or sun in various mythologies across the world. I'm probably going to have to make a mega-post about snakes and serpents in Genshin at some point.
Nahida calls herself "just the Moon" when we first meet her. In context, she means that she is only a reflection of Rukkhadevata's former glory, but I still find it relevant that she calls herself the moon when her appearance is so similar to what the Moon Sisters are supposed to look like.
The description for the Nilotpala Lotus refers to a moon goddess (singular) and the chariot. Nilotpalas only bloom at night. (It's interesting that the "fake" lotus, Kalpalata, is Nahida's ascension material and not the Nilotpala.)
The lore for the Xiphos' Moonlight sword suggests that the Moon Sisters were capable of "determining heroes' fates." This is most likely a reference to the three Fates of Greek mythology, who controlled the birth, life and death of all humans.
Aaand most recently, in Lyney's character teaser, we get to see him holding the full moon in his hands! In the Rider-Waite tarot, the Moon is a symbol for lies, deception and illusion. This doesn't just have to apply to Lyney - it's something I've been thinking about for as long as I've known about the Moon Sisters.
if you have any specific questions or want more clarification on any of this info, PLEASE ask!!!