Short answers, pulled from the story.
Ancient Egyptian religion was a complex system of polytheistic beliefs and rituals that formed an integral part of ancient Egyptian culture. It centered on the Egyptians' interactions with many deities believed to be present and in control of the world. About 1,500 deities are known.
Ma'at was the fixed, eternal order of the universe in ancient Egyptian religion, encompassing truth, justice, and order, and was often personified as a goddess. It had existed since the creation of the world, and without it the world would lose its cohesion. The pharaoh and all of society were required to maintain it and repel Isfet, which was chaos.
Ancient Egyptian religion had its roots in Egypt's prehistory and lasted for 3,500 years. The religion decentralized following the Roman conquest of Egypt in 30 BC and was suppressed during the Christian period. It was conventionally considered to have fully died in the 530s.
Akhenaten was a pharaoh of the New Kingdom who replaced Amun with the sun-disk Aten as the state god and eliminated the official worship of most other gods. He moved Egypt's capital to a new city at Amarna and claimed that only he could worship the Aten. His successors restored the traditional religion and dismantled all Atenist monuments, and Akhenaten came to be reviled as a heretic.
Ancient Egyptians believed each person had a ka, or life-force, and a ba, a set of unique spiritual characteristics, which funeral rituals reunited so the person could live on as an akh. Preservation of the body by mummification was central, because the ba was thought to return to its body each night. In the New Kingdom, the soul faced a final judgement called the Weighing of the Heart, carried out by Osiris and the Assessors of Ma'at.
State-run temples served as houses for the gods, where images acting as their intermediaries were cared for and given offerings to sustain the gods so they could maintain the universe. Ritual duties were almost always carried out by priests, and professional priesthood became widespread only in the New Kingdom. As temple wealth grew, the high priests of Amun at Karnak became the effective rulers of Upper Egypt during the Third Intermediate Period.
The temples at Philae were closed officially in AD 537 by the commander Narses the Persarmenian on an order of the Byzantine emperor Justinian I, an event conventionally considered to mark the end of ancient Egyptian religion. A study by Jitse Dijkstra argues organized paganism at Philae ended in the fifth century, while a petition from Dioscorus of Aphrodito dated to 567 suggests some adherence survived into the sixth century.