Commenting on the Assyrian “metru” Professor Moulton says: “If this is his (Mithra's) origin, we get a reasonable basis for the Avestan (Early Persian and Aryan) use of the word to denote a ‘contract’, as also for the fact that the deity is in the Avesta patron of Truth and in the Veda of Friendship. He is ‘the Mediator’ between Heaven and Earth, as the firmament was by its position, both in nature and mythology: an easy corollary is his function of regulating the relations of man and man.” The character of an imported deity is always influenced by localization and tribal habits. Pastoral nomads would therefore have emphasized the friendliness of Mithra, who sent rain to cause the growth of grass on sun-parched steppes. Both Mithra and Varuna had their dwelling-place in the sea of heaven, the waters “above the firmament” from which the rain descended. Ultimately the Indian Mitra vanished, being completely merged in Varuna, who became the god of ocean after the Aryans reached the sea coast. In post-Vedic sacred literature the priestly theorists, in the process of systematizing their religious beliefs, taught that a great conflict took place between the gods and demons. When order was restored, the various deities were redistributed. Indra remained the atmospheric god of battle, and Varuna became the god of ocean, where, as the stern judge and lawgiver and the punisher of wrongdoers, he kept watch over the demons. In the “Nala and Damayanti” epic narrative, the four “world guardians” are: Indra, king of the gods; Agni, god of fire; Varuna, god of waters; and Yama, judge of the dead. It may be that the displacement of Varuna as supreme deity was due to the influence of the fire-worshipping cult of Agni, who was imported by certain unidentified Aryan tribes that entered India. Agni did not receive recognition, apparently, from the other Aryan “folk-wave”, which established a military aristocracy at Mitanni in Mesopotamia, and held sway for a period over the Assyrians and some of the Hittite tribes. An important inscription, which is dated about 1400 B.C., has been deciphered at Boghaz-Köi in Asia Minor by Professor Hugo Winckler, who gives the names of the following deities: “Mi-it-ra, Uru-w-na, In-da-ra, and Na-sa-at-ti-ia”— Mitra, Varuna, Indra, Nasatya. The latter is Nasatyau, the Vedic Aswins, twin gods of morning, who have been compared to the Greek Dioskouri (Castor and Pollux), sons of Zeus. A Vedic triad, which suggests a rival cult to that of the worshippers of Varuna and other Adityas, is formed by Vayu (wind), Agni (fire), and Surya (the sun). The Indian sun god Surya, like the Egyptian Ra, had three forms. The rising sun was Vivasvat; the setting sun was Savitri. Vivasvat was the son-in-law of Twashtri, the artisan of Nature; he was an abstract deity, and apparently owed his origin to the group of Adityas.