Rosalyne-Kruzchka Lohefalter, also known as La Signora and by her codename "The Fair Lady," was the Eighth of the Eleven Fatui Harbingers, and a supporting antagonist in the early chapters of the Archon Quests. She is the first Harbinger to appear in the game when she ambushes and overpowers Venti to steal his Gnosis. Her attack leaves a lasting impression on the Traveler, who greatly distrusts the Fatui and their intentions after witnessing said event.
Five hundred years ago, before she became a Harbinger, Rosalyne was an ordinary young woman from Mondstadt who studied at Sumeru Akademiya. When her lover Rostam died during the cataclysm, Rosalyne was consumed by anguish and hatred and used the art of liquid fire to transform her body into that of living flame, thereafter becoming known as the Crimson Witch of Flame.
Ultimately, she lost to the Traveler in their duel before the Raiden Shogun's throne, and was subsequently executed by the Musou no Hitotachi.