Ulgen, honoured with the title Bai-Ulgen, "rich Ulgen" or "great Ulgen", is the principal benevolent sky deity of Altai Turkic shamanism, credited in South Siberian creation narratives with shaping the visible world and standing as the source of light, order and goodness against Erlik's rule of the underworld below. Ulgen occupies a central place in the Altai shaman's ecstatic practice specifically because he is understood to dwell at the highest of several successive sky levels, and Siberian ethnographic accounts describe the shaman's ritual seance as a literal ascent, level by level, often dramatised through climbing a birch pole or tree notched to represent each stage of the sky, culminating in a direct address to Ulgen at the top on behalf of the community, most often to request good fortune, healthy livestock or the recovery of a sick person's soul. This vertical cosmology, sky above organised in ascending tiers with Ulgen at its summit and an underworld below organised in descending tiers with Erlik at its depth, is one of the clearest and best documented instances anywhere of the layered cosmic map many scholars consider a defining structural feature of Siberian and Inner Asian shamanism generally.