It was doubtless the association of Nebo with Merodach that caused him, like Thoth in Egypt, to become the patron of literature and the god of the scribes. The culture-god was as it were divided into two; while Merodach retained the functions peculiar to a Semitic Baal, Nebo watched over the library and school, and encouraged the study of the script which had been invented by him. The older claims of Ea fell into the background and were forgotten; it was no longer the god of Eridu, but Nebo, who had written the first book, and instructed mankind in the elements of culture. The marshal's staff, which Nebo had wielded as organiser of "the hosts of heaven and earth," now became the rod of the scribe, and a consort was created for him in the person of Tasmit or "Hearing." In Assyria, where the worship of Assur prevented any development of that of his rival Merodach, Nebo became a special favourite of the literary class, who derived their knowledge and inspiration from Babylon. Assur-bani-pal never wearies of telling us how Nebo and Tasmit had "made broad his ears and enlightened his eyes," so that he had collected and republished the books and tablets of the kings who had gone before him.
As minister of Merodach, Nebo passed into the solar circle. In Egypt he would have been absorbed by the more influential god, but in Babylonia the Semitic conception of Merodach as a Baal who required his minister and envoy like an earthly king, stood in the way of any such identification. He consequently retained his personality, and it was another god who was identified with him. This was Nusku, once the fire which blazed up into flame and purified the sacrifice. With the spread of the solar cult Nusku became a local sun-god, and was regarded as the god of the burning sun of noon. In Sumerian days, however, while he was still the spirit of the fire, he had been necessarily the servant and associate of En-lil; and when En-lil became the Semitic Bel of Nippur, Nusku followed his fortunes and was made his messenger. After this his identification with Nebo was easy. Nebo, too, was the messenger and interpreter of Bel, though it was the younger Bel of Babylon who had supplanted the older Bel of Nippur. As Bel-Merodach took the place of En-lil, so too did Nebo take the place of Nusku. The priests of Babylon knew of one Bel only, and the minister of Bel must be one and the same whether his name were Nusku or Nebo. That Nusku had originally been an independent deity was, however, never forgotten. The past history and religion of the country could not be ignored, and the priesthood were forced to erect a separate shrine to Nusku within the precincts of the temple of Nebo itself. Only thus could they be certain that the god would not avenge himself for being defrauded of his dues.