Koitar and Boreas (mural in Amsvartnir
This mural is so beautiful, it’s my lockscreen wallpaper for the time being :)
Quick lore refresher for anyone who didn’t pay too much attention:
Koitar was the first Angel (Seelie, the same race as Nabu Malikata and Nicole). The artisans of Hyperborea used her methods to create the Fae (the race which Flins and Linnea belong to).
Koitar was appointed as divine envoy to Hyperborea and she dwelled underground near Irminsul. She was visited one day by Seutervoinen (voyager from the Sea of Stars) who questioned why the pursuit of knowledge was deemed sinful. He asked Koitar about the origins of Teyvat and shared the truth of his own origins (his consciousness). Koitar was stunned by this revelation, and her crown broke as she felt true love and freedom from the grasp of the Heavenly Principles. She shared the secrets of creation with Seutervoinen and he vowed to stand alongside her in a rebellion against the Heavenly Principles. Koitar and Seutervoinen took control of Hyperborea and granted them knowledge of advanced technology, encouraging them to explore the Sea of Stars beyond the False Sky. They ruled for a decade before the city was inevitably punished by the Heavenly Principles in the form of a Celestial Nail during the War of Funerary Flame. Koitar and Seutervoinen were captured by the Heavenly Principles and punished; Koitar’s kin were to lose their minds and physical forms should they ever fall in love.
Koitar was confined to the Royal Court of the Seelie (the ruins above Amsvartnir where the pictured mural can be seen) where she wept for her own misery with her kin (the seelies) who she could no longer recognise. While imprisoned, she encountered the wolf we know as Boreas (from the Greek “Voreas”, North Wind), and she found him pleasing to look at, allowing him to reside with her and even giving him his aforementioned name. Boreas gained human speech and intellect under her teaching (or blessing) and came to view Koitar as a maternal figure. Boreas requested to depart for the South to aid its kin and Koitar did not refuse. Through Boreas, she maintains memory of her beloved and of the Heavenly Principles’ cruelty.
Source: Genshin Impact wiki, in-game sources