Marital Vows of Rainbow Skirts and Feather Robes (霓裳羽衣 比翼連理?) is the Noble Phantasm of Yang Guifei. A passage from the chinese poem "Song of Everlasting Regret" in which Bai Juyi told of the immortal love of Emperor Xuanzong and Yang Guifei. "Rainbow Skirts and Feather Robes" was wriiten by Xuanzong for Yang Guifei. As it was a song that symbolized the forbidden love of a ruler towards a beauty that could lead said ruler astray, the song was shunned by others and became lost in time.
Prior to marriage she became a Taoist nun of considerable position and learned from the Taoist Luo Gongyuan, receiving the title Taoist Taizhen. After death that soul became an immortal (xian) of Mount Penglai. It is said that she is still waiting in Mount Penglai to be reunited with the Emperor she dearly loves. The star of the abyss secretly chants a melody that does not reach the ears of the common folk.