Harmonious Jade is a Solar Exalt in the Age of Sorrows, and the signature Night Caste in First and Second Editons.
Jade was born in the South and enslaved by a Yozi cult as a small child. Raised to worship Sondok and work as a thief, she knew nothing outside the cult. On one particularly difficult mission, Harmonious Jade was Chosen by the Unconquered Sun. She had no idea the Solars were the Yozis' ancient enemies, so she simply returned to the cult and told them what happened.
Fortunately, the cult leader was a particularly stupid fanatic who valued idealogical purity over the chance to give the Yozis a Solar Akuma. He ordered his cult to attack the new Lawgiver, who promptly escaped. Harmonious Jade became an enemy of the Yozi cult, and joined a Solar circle consisting of Dace, Panther, Arianna, and Swan.
She is the reincarnation of the Solar Gold-Shadowed Arrow. She eventually met the Day Caste Abyssal called Disciple of Seven Forbidden Wisdoms, the reincarnation of Gold-Shadowed Arrow's lover in the First Age. The two may have struck up a relationship.