In The Celestial Empire, I briefly mentioned them in the section about Chinese Myths and Beliefs (p34-35). In particular, I have written the following on p35:
Evil whitesouls are brought to the ten infernal tribunals, ruled by the ten Yāma Kings (閻王 Yánwáng), the judges of the Nether Region, who decide the kind of punishment to be undergone in the City of Ghosts (Fēngdū 酆都).
The scope of this blog entry is to give some more detail about the Ten Yāma Kings and their halls, should your foolish players travel to the Underworld!
Here is the roster:
1 - the King of Qínguǎng (秦廣王蔣). He rules the very first hall and is responsible for a preliminary review of the deeds from the whitesoul's lifetime. The actual punishment is then carried out in one of the nine other halls.
2 - the King of Chǔjiāng (楚江王歷). He rules the court reserved for thieves and murderers, and his hell is ice cold.
3 - King Sòngdì (宋帝王余). He rules Black Rope Hell.
4 - King Wǔguān (五官王呂). He rules Blood Pool Hell.
5 - King Yāma (閻羅王包). He rules the Iron City and oversees the nine other Yāma Kings.
6 - King Impartial (平等王陸). He is in charge of discriminating between ghosts according to their behaviour, and deciding affairs such as grades and transmigration.
7 - the King of Mount Tài (泰山王董). He rules the Black City of Shadowy Fiends. He is No.2 in the hierarchy of the Yāma Kings.
8 - the Metropolitan King (都市王黃). He rules the Suffocation Hell and the City of the Dead-by-Accident.
9 - the King of Biànchéng (卞城王畢). He rules the City of Innocent Deaths.
10 - the King of the Ever-Turning Wheel (轉輪王薛). He rules the tenth and last hall and is responsible for meting out retribution. Like in the first hall, there is no place of torment here. The Terrace of Oblivion is part of the tenth hall.
Note that depending on the sources, the order of the judges between 6 and 9 is not always the same.