Atum is the Heliopolitan creator, the first god, who emerged self-made on the benben mound out of the waters of Nun. He produced Shu and Tefnut - sneezed or spat out in the Pyramid Texts, masturbated in other accounts - and so began the Ennead. He is the evening sun, the 'Complete One' who receives the dead king and returns to the waters at the end of the cycle, and in the Book of the Dead he rises from chaos in serpent form.
Modern Practice
Atum is worked with at the close of a thing - a project, a year, a life - and at the solitary beginning that has no precedent. Modern practice keeps the Egyptian frame: a clean surface, cool water, and speech rather than symbol.