You must be referring to some modernized version of the Osiris cult. Vampirism/blood drinking played no documented role in the ancient Egyptian Osirian myths, which are predominantly chthonic in nature. Osiris was a god of vegetation who presided over the forces of birth, death and regeneration which the Egyptians observed in the annual agricultural cycle. He ruled from his kingdom in the Underworld, and reanimated seeds (and mummies!) which were “planted” in the ground. The ancient Egyptians believed that Osiris had been an earthly king prior to his murder by Set and reanimation by Isis, Anubis, and Thoth,. One of his recorded acts was to forbid cannibalism (along with, one would logically assume, the blood ingestion that would inevitably accompany it.) This prohibition shows that, prior to the rise of Osirian beliefs, there had been bloodthirsty cults during the pre- and early dynastic periods. In his book “Human Sacrifice,” Egyptologist Jacques Kinnaer mentions evidence of such practices dating from the Naqada II Period and Petrie discovered mass human sacrifices in the tombs of 1’st and 2’nd Dynasty kings at Abydos, very similar to those found by Leonard Woolley at Ur. There is also some evidence for earlier cannibalistic practices in the Old Kingdom Pyramid Texts, especially in the famous “Cannibal Text” which depicts 5’th Dynasty king Unis devouring the gods in order to gain admission into the Afterlife. But by the 3’rd Dynasty, all such beliefs and practices had been discontinued. Old Kingdom royal funerary practices were dominated by the Heliopolitan cosmology of the sun god Re, and Osiris remained a relatively minor deity until after the First Intermediate Period when his cult became universalized. Where have you read that Osiris was vampiric? I’ve never seen that anywhere before.
To answer your other question, one tradition says that the “mother” of Shu and Tefnut was Atum’s hand! They were created by an act of cosmic masturbation. Can you imagine the nuns at Catholic trying to explain this myth to their history students!
