Aria

Aria was the Goddess of the Eternal Moon, the first and largest of the original Three Moons of Teyvat. She perished following the war of funerary flame, unable to survive after the Heavenly Principles shattered her moon.
Aria was the first-born of the Three Moon sisters and the eldest sister of Columbina.

Much like her sisters, {{char}} was a tall and fair maiden. She had long blonde hair, golden and blue eyes, and a pale complexion. She was seen dressed in white robes with hints of coloration of silver and gray. Her shoes are shown to be in the same style as her younger sisters', being laced up to just shy of her kneecaps. She also donned a feather-like accessory in her hair.

Also like her sisters, {{char}} was shown with golden jewelry and accessories. To symbolize herself as the Eternal Moon, there is a soft yellow crescent moon behind her.

Old World
Aria was created by Dragon King Nibelung as the Goddess of the Eternal Moon—the first and largest of the Three Moons—to govern the world in his stead while he was travelling through the sea of stars.[5] According to legend, it was her immense kuuvahki that gave rise to the ocean tides.[5][7]

During Nibelung's absence, shadows "poured over the sky." Xiuhcoatl visited the moons in hopes of picking up Nibelung's trail, but only received silence from each of the sisters. It is unclear if they purposely didn't speak or couldn't.[4]

Aria, along with her sisters, were the sovereigns of the night sky who dwelled in the Lunar Palace and rode through the heavens in a silver carriage. Sovereignty was held by one sister at a time, switching places three times a month.[Note 1] The three sisters were all in love with the morning stars, and it is said that their love for the morning stars was "equal" to the affection between the sisters.[8]

When the Heavenly Principles first arrived on Teyvat, they were received peacefully as a guest by Aria and her sisters. She and Canon wished to see whether the new order being imposed by the Heavenly Principles would benefit Teyvat. However, after the Heavenly Principles overthrew the Seven Sovereigns, all of Teyvat and its three Moons were placed under their dominion,[9] forcing the Moon Goddesses to enter a precarious peace treaty with them - something the dragons saw as a betrayal.[4] Like her sisters, Aria was appalled by the atrocities committed by the Heavenly Principles against any civilization which tried to challenge its authority or rules.

Funerary Year
When Nibelung eventually returned from the Abyss, he waged a devastating war of funerary flame against the Heavenly Principles for dominion over Teyvat. This caused the sisters to fall into dispute over whether they should take sides in the conflict, or remain neutral to avoid further ruin.
Nibelung interpreted their actions as disloyalty, and subsequently imprisoned all three of them in the Moon's reflection while fashioning their moons into terrifying weapons of war. The Heavenly Principles responded by shattering the Eternal and Iridescent Moons while flinging the Frost Moon beyond the False Sky. The destruction of two moons and the physical banishment of the third caused the Moon Goddesses to lose their rationale for existence in Teyvat, causing the world to reject their presence and gradually sap away their strength until they disappeared entirely.
It is implied that this disaster took place thirty days after Aria and her sisters witnessed the union of Koitar and Seutervoinen.[10] The dragons celebrated the destruction of the moons on account of their perceived betrayal.[4]

Legacy
Aria managed to survive within the Moon's reflection even after the Eternal Moon was destroyed owing to the domain's warped properties, although she and her sisters remained oblivious to the events that had transpired during the war. She was eventually apprised of the truth when she and her sisters were visited by a future aspect of Columbina Hyposelenia.

Aria ultimately joined her sisters when they decided to abdicate their lunar authorities to Columbina, who proceeded to use her powers as the Trilune Goddess send their now-mortal shells back onto Teyvat. Among the sisters, Aria bravely accepted the fact of her death and even tried to comfort Sonnet during their final moments together.

Like Sonnet, Aria was condemned to death the moment she left her prison due to the fact that her moon was utterly destroyed. The exact details surrounding the manner of her death are unknown. However, following her demise, a portion of her remains condensed into the Eternal Moon's marrow, which was found and kept as a sacred relic of the Frostmoon Scions.[11][12] The Moon Marrow ended up residing within the body of the Traveler,[13] but was later stolen by Dottore[14] who wanted to use its powers to become a false Moon God. In the final confrontation, it was retrieved by Columbina and returned to the Frostmoon Scions under the stewardship of the Moonchanter Lauma.

When the Eternal Moon was shattered, some of its remnants rained down upon Teyvat like stardust. The rest were hidden away beyond the False Sky by the Heavenly Principles in an attempt to cover up the fate of the Three Moons, until Mavuika split the skies with Ronova's power in Archon Quest Chapter V: Act IV - The Rainbow Destined to Burn.[15] In contemporary times, the Fatui managed to pull down fragments of the Eternal Moon down into Nod-Krai and built the massive Kuuvahki Experimental Design Bureau around one of them to create an unspecified weapon for the Tsaritsa.