“The trinity consisted of the god Serapis (=Osiris+Apis), the goddess Isis/Ishtar (= Hathor, the cow-moon goddess), and the child-god Horus (the Egyptian Tammuz). In one way or another almost every other god was identified with one or other of these three aspects of the one god, even the sun god Mithras of the Persians (whom Constantine worshipped). The origin beginning with Baal, Ishtar, Tammuz of the ancient Babylonian Religion. Many of the theories of Egyptian religion have penetrated into the theology of Christian Europe, and form, as it were, part of the woof in the web of modern religious thought. Christian theology was largely organized and nurtured in the schools of Alexandria, and Alexandria was not only the meeting place of East and West, it was also the place where the decrepit theology of Egypt was revivified by contact with the speculative philosophy of Greece. Perhaps, however, the indebtedness of Christian theological theory to ancient Egyptian dogma is nowhere more striking than in the doctrine of the Trinity. The very terms used of it by Christian theologians meet us again in the inscriptions and papyri of Egypt. Originally the trinity was a triad like those we find in Babylonian mythology. The triad consisted of a divine father, wife, and son. This triune god was later formulated into Christianity as the Christian Trinity of father, son, holy ghost.” * Excerpt from the book Abstract
According to the Helipolitan tradition, Osiris was granted the throne of Egypt rather than his elder brother Set. Set was none to pleased about this, but became enraged when Osiris left Egypt to travel the world and left Isis in charge of the Kingdom instead of him. Set decided to get rid of his brother and take the throne for himself. Although the myth of the origins of Anubis is a later development it was also cited as one of the reasons why Set was jealous of his brother Osiris and conspired to kill him. Set tricked Osiris into climbing into a wooden chest cut to fit him and then sealed the box and threw it into the Nile. Isis searched everywhere for her husband’s body and found it lodged in a tamarisk bush which had grown into a huge tree on contact with the body of the god. She broke open the chest and carried his body back to Egypt.
She placed the body in the temple and transformed herself into a kite (a small bird) and flew over the body singing a song of mourning. She then used her prodigious magical talent to conceive Heru-sa-aset(Horus, son of Isis), whose destiny was to avenge his father and defeat Set. Isis then implored Thoth for his help in resurrecting Osiris. The two deities composed the “Ritual of Life”, the spell which granted eternal life after death. However, Set discovered their plans and stole Osiris’ body. He split it into fourteen pieces and scattered them throughout the length and breadth of Egypt. Still Isis refused to be beaten. She enlisted the support of her sisterNephthys to find the pieces and the help of Anubis to prepared the body (in the first mummification). When the “opening of the mouth” ceremony was performed, Osiris’s spirit returned to his body.
However, no spirit which has passed to the land of the dead may live in the land of the living, and so Ra decreed that Osiris should become the King of the underworld, and Anubis agreed to give up his position as the lord of the netherworld out of respect for Osiris.
Meanwhile Isis hid with her infant son in the marshes of the delta, protecting him until the day when he could face Set and recover his father’s kingdom.
When Horus came of age he battled with his uncle. Isis used her magic to assist Horus in battle, but when the opportunity presented itself she could not kill Set, who was after all her elder brother. This enraged Horus, who promptly lopped off her head! Isis was apparently unperturbed by this turn of events, and caused a cow’s head to grow on her shoulders. Fortunately for Horus, Isis forgave his unreasonably aggressive reaction and continued to support him. http://ancientegyptonline.co.uk/isiso.html