Boreas Presence quest

probably, but the quest itself was about the bloodstained knight Roland descent into madness perhaps they will tie Boreas and Roland in some lore somehow.

I don't think the angel in the mural is ever mentioned by name in that world quest, but it's heavily hinted at that she was Koitar, the first angel who rebelled against the heavenly principles and doomed the Angels to become Seelie if they fall in love. Based on the two bits of "ancient handwriting" inside the castle with the mural, this is after the Angels were punished. She is self aware enough to play her lyre and weep for the tragedy of her people, but she doesn't remember who she is and doesn't recognize the Seelie around her. She is essentially imprisoned inside the castle where she stays.

Some time after the Angels became Seelie and prior to - or during - the Archon Wars, she notices "Storms came from the south, cold came from the north. That beast came from the north, bearing the chill of ice and snow." Andrius arrives and stays a while to listen to her song. He initially couldn't speak and sat with her for a while, and she found him amusing and gave him the name Boreas. He gained intelligence and wisdom alongside the capacity to speak and learned to treat others with kindness and sincerity. Boreas called her Mother, and decided to go south to help the people there. She bid him farewell and that's the last we know of whatever happened to her.

We, of course, know that Boreas went south and fought with Decarabian, the God of Storms, who was a tyrant king of Mondstadt. Decarabian was defeated by his own people with the help of Venti who then became the Anemo Archon, and Boreas died willingly so his spirit would become one of the 4 winds protecting Mondstadt.

not true. so far its been minuscule things that do not give extra rewards but Flins being the first so far has activated an anecdotal world quest that is only available to him may change when illuga drops but