Yamaraja, the Vedic lord of death.
The ruler of the great hell is called Yama or Yamaraja.
But there is not only one Yamaraja for one Mahaniraya; there are actually four Yamaraja who are in charge of the four gates.
Thus for eight great hells there are altogether thirty-two Yamaraja.
Apart from these Yamaraja there are a number of hell-guardians called Niraya-pala.
The duty of the Yamaraja is to consider the case of each hell creature and give orders for punishment;
the Niraya-pala’s duty is to inflict the penalties typical of each hell on the hell-creatures.
Yamaraja and Niraya-pala are actually not hell beings but belong to the heaven of Catummaharajika.
They are described as Vemanikapeta, the beings that sometimes enjoy the fruitions of their meritorious kamma in heaven and sometimes suffer the results of their evil deeds in hell.
By particular kinds of karma they are sent to perform their duties in this realm of misery by inflicting penalties on the hell creatures.