Qin Guang Wang, or King Qin Guang, resides in the First Court of Di Yu (地狱 dì yù), he is Ruler of Di Yu, and Keeper of the Book of Life and Death (生死簿 shēng sǐ bù). This position was once held by Yan Luo Wang (阎罗王 yán luó wáng) before he was demoted to the Fifth Court of Di Yu by the Jade Emporer (玉帝 yù dì) for being too merciful.
As the ruler of Di Yu, Qin Guang Wang passes judgement on the souls (魂 hún) that are brought to his Court by his servant demons, Ox-Head and Horse-Face (牛头马面 niú tóu mǎ miàn).
In order to help him pass judgement, Qin Guang Wang places each soul in front of a mirror called Nie Jing Tai (孽镜台 niè jìng tái) – a mirror which shows a reflection that is a representation of the persons’ sins, not of the physical body – and will pass judgement in accordance with what he sees. In English, the mirror is often referred to as the “Mirror of Retribution.”
As the Ruler of Di Yu, Qin Guang Wang presides over 9 other Yama. Each Yama govern their own Court and pass judgement on a soul in accordance with the sins committed that are under their jurisdiction.
To read more on Di Yu, check out my blog: A Journey Through Di Yu - "Chinese Hell"