Ossetian water-deity; Lord of the Sea / Lord of the Waters. The Iranic-Caucasian reflex of the Indo-Iranian Apam Napāt ("Grandson of the Waters"), preserving the Avestan and Rigvedic water-deity figure within the Nart-saga frame. Father of Dzerassae and progenitor of the maternal line of the central Nart heroes (Uryzmæg, Khæmyts, Satana). The medieval Christian-syncretic name-element "Bettyr" (Peter) reflects the late overlay of Caucasian-Christian saint-veneration onto the older Iranic substrate; the Christian Pyatnitsa-Friday-Peter complex partially syncretized with the older water-deity through the festival calendar. The underwater kingdom of Donbettyr — variously located in the Caspian or Black Sea in different recensions — is the maternal-genealogical anchor of the Nart cycle and a recurring narrative space for hero-questing episodes (Akhsartæg's pursuit of the dove-Dzerassae into the underwater realm, Uryzmæg's descent to retrieve Soslan from Donbettyr's court, etc.).