Yama is the God of the Underworld, Lord of Secrets and Judgment. He is often associated with decay although he is not the god of death. Yama is mysterious to most of the races of the Whorl. He maintains the deep places below the surface where ancient machines engage in unknown functions and where the unwary might stumble upon a portal to the Endless Void and go mad.
Because his realm is so far below civilized lands, Yama was not widely worshiped before the War in Heaven and Earth. When Surya rebelled against Mahadeva, Yama stayed aloof and neutral. Although Indra resented that neutrality (and still does) it meant that when the war was over only Yama was in a position to arbitrate the settlement of outstanding grievances and preside over the just aftermath of the war.
As a result of this role, Yama assumed a certain aspect of Justice and Law. In the millenia after the Godswar, temples to Yama have sprung up in various nations, all providing arbitration and mediation services, moving into territory that was once Durga's alone. In some lands, the rulers have abdicated judgment for crimes entirely to Yama's priesthood.
Yama's realm is the Underworld, the physical network of endless deep tunnels that lie beneath the surface of the entire Whorl.
Yama, when he is depicted at all, is shown as an emaciated, or sometimes even rotting figure with obscured features. He is more typically represented with the simple symbol of the balanced scales of justice.