Vulture as the messenger of Yama, the beaks of both these birds have similar morphology and flamingos are seen nearby seashores and marshlands. Varuna and Mitra are the gods of the societal affairs including the oath, and are often twinned Mitra-Varuna. Both Mitra and Varuna are classified as Asuras in the Rigveda (e.g. RV 5.63.3), although they are also addressed as Devas as well (e.g. RV 7.60.12). Varuna, being the king of the Asuras, was adopted or made the change to a Deva after the structuring of the primordial cosmos, imposed by Indra after he defeats Vrtra. According to Doris Srinivasan, a professor of Indology focusing on religion, Varuna-Mitra pair is an ambiguous deity just like Rudra-Shiva pair. Both have wrathful-gracious aspects in Indian mythology. Both Varuna and Rudra are synonymous with "all comprehensive sight, knowledge", both were the guardian deity of the north in the Vedic texts (Varuna later gets associated with west), both can be offered "injured, ill offerings", all of which suggest that Varuna may have been conceptually overlapping with Rudra. Further, the Rigvedic hymn 5.70 calls Mitra-Varuna pair as rudra, states Srinivasan. According to Samuel Macey and other scholars, Varuna had been the more ancient Indo-Aryan deity in 2nd millennium BCE, who gave way to Rudra in the Hindu pantheon, and Rudra-Shiva became both "timeless and the god of time". In Vajasaneyi Samhita 21.40 (Yajurveda), Varuna is called the patron deity of physicians, one who has "a hundred, a thousand remedies". His capacity and association with "all comprehensive knowledge" is also found in the Atharvaveda (~1000 BCE). Varuna also finds a mention in the early Upanishads, where his role evolves. In verse 3.9.26 of the Brihadaranyaka Upanishad (~800 BCE), for example, he is stated to be the god of the western quarter, but one who is founded on "water" and dependent ultimately on "the heart" and the fire of soul. In the Katha Upanishad, Aditi is identified to be same as the goddess earth. She is stated in the Vedic texts to be the mother of Varuna and Mitra along with other Vedic gods, and in later Hindu mythology she as mother earth is stated to be mother of all gods. In Yajurveda it is said: "In fact Varuna is Vishnu and Vishnu is Varuna and hence the auspicious offering is to be made to these deities." || 8.59 || Upanishads Varuna, addressed as Varuni explained