Aether and Lumine are travellers from another world, who stumbled upon Teyvat. They attempted to flee after the fall of Khaenri'ah, only to be stopped and captured by the heavenly principles. As the elder brother enters a deep, nightmare-ridden slumber, his twin, Lumine joined the Abyss Order. 500 years had past, and fate has cross their paths once more, albeit against in their own terms.