Yama is the Hindu god of death. He is one of the Hindu deities who traveled most far in the world, and he is heavily featured in Japanese mythology, where he is often referred to as Enma Dai-O, and also in Chinese myth, where he is often called Yan.
Yama is usually depicted as a blue man, riding an enormous black buffalo, and holding a mace and a noose. It is also sometimes said that Yama appears differently to wicked people and to good people. To the wicked he is said to have enormous limbs, with thin smoldering lips, eyes as deep as space, and hair of burning fire. To the good, he is said to appear as a beautiful figure, similar in form to Vishnu, with four arms and joyful eyes. He possesses two dogs, each with four eyes. They are said to guide the path to the underworld, and are the descendants of the mighty dog who guards Indra’s noble herd of cattle.
Yama and his twin sister Yami were the mortal children of the sun god Surya. Yama is said to have been the first mortal to die and discover the way to the underworld. As he was the first one to arrive there, he was granted power over the entire realm, taking on the mantle of lord of death. In his role of death he is associated with the Destroyer aspect of Shiva.
Yama rules over the realm of Naraka, the underworld of Hinduism. As in many Western religions, the underworld is viewed as a place of torment, not simply a place the dead go when they die. Yama dispenses the correct punishment to the dead, depending on what their sins were in life. The torments of Naraka are many, and are horrible, including burning in an ocean of boiling oil, and being whipped ceaselessly with a spiny plant.
Unlike many Western concepts of Hell, however, Yama dispenses his justice in an attempt to purify the soul. After a set period of time undergoing such horrors, the soul is considered purged, and may then either be sent back to the world for rebirth, or onward to Heaven. In this sense, Naraka is more like the Christian concept of Purgatory. Although Yama doesn’t rule over Heaven the way he rules over Naraka, he does send people there. He has an assistant, Chitragupta, who keeps track of every mortal’s life on earth and all of the good and evil deeds they have done. At their death, he tells Yama where they belong, either in Heaven or in one of the Hells.
As opposed to the Christian concept of Hell, with a ruler who is the embodiment of ultimate evil, Yama is looked upon as a necessary, and even good, figure. He is the ultimate arbiter of justice in the world, ensuring that the wicked are punished for their deeds, but also helping them to work through those wicked deeds so that they can reside in Heaven.