The serpent god Nhb-Kaw whose name means "He-who Harnesses-the Spirits", was first attested in the Pyramid Texts and was regarded as a benign and helpful deity. He assisted the deceased king in various ways and seems to act as an intercessory on his behalf.The god was believed to be the son of the scorpion goddess Serket, though an alternative tradition claimed that he was the son of earth god Geb and the serpent Harvest goddess Renenutet. His chthonic origins and serpentine nature-coupled with "seven cobras" he is said to have swallowed- are the source of Nhb-Kaw's considerable power. This is seen in later texts which assert that Nhbu-Kaw is not subject to any harmful magic and cannot be harmed by water or fire. The god's consort was thought to be Nehemtawy⁽[1]⁾. He was at one point a rather fierce and aggressive deity, and so the god Atum had to press his nail into Nhb-Kaw's spine, so he could control the serpent god. The ancient Egyptians believed that he could not be overcome with magic, fire or water⁽[2]⁾.
([1])Ch.  Leitz, Lexikon der Ägyptischen Götter und Götterbezeichnungen VI (Germany, 2002), 283; R.H.  Wilkinson, The Complete Gods and Goddesses of Ancient Egypt (Cairo, 2003), 224.. ([2])A.W.  Shorter, The God Nḥb-Kɜw, Journal of Egyptian Archeaology 21 (Cairo, 1935), 41-48.