Just before the violent Doric invasions, the Achaeans fought the Trojans of Asia Minor. The chronicle of that war, the Iliad, furnishes the first clear picture of the early Greek religion as it evolved from a blending of Achaean, Dorian, Minoan, Egyptian, and Asian elements. This phase of Greek religion is called Homeric, after the author of the Iliad, or Olympian, after Mount Olympus, the Thessalian mountain where the gods dwelled. The early Egyptian influences represented by half-human, half-animal deities vanished, and the Olympians were purely anthropomorphic figures. Zeus was the supreme lord of the skies, retaining his original Aryan importance; he shared his dominion with his two chthonic and pre-Aryan brothers, Hades, lord of the underworld, and Poseidon, lord of the waters.
Through a vast set of myths and legends (the clearest illustration is Hesiod's Theogony ) the other gods and goddesses were carefully related to one another until a divine family was established with Zeus as its titular head. The Homeric pantheon was a tightly knit family group in charge of natural forces but not equal to the natural forces themselves. The gods had supernatural powers (particularly over human life), but their power was severely limited by a concept of fate (Moira) as the relentless force of destiny. The gods were not thought to be omnipresent, omniscient, or omnipotent. Shorn of the usual godly attributes, the Olympians often took on the property of being simply bigger than humans, but not different or alien. The Olympians fought one another and often meddled in human affairs (this intervention was called the deus ex machina, or divine intervention).
The superhuman features of the Olympians were their immortality and their ability to reveal the future to humanity. The Greeks did not consider immortality a particularly enviable property. Action was crucial and exciting by the very fact of life's brevity, and people were expected to perform by their own particular heroic arete, or virtue. Death was a necessary evil; the dead were impotent shades without consciousness, and there are only vague images of the Isles of the Blest in an Olympian world. The Greeks, however, did expect information about their future life on earth from the gods. Thus divination was a central aspect of religious life (see oracle).
The Olympians were, perhaps, most important in their role as civic deities, and each of the Greek city-states came to consider one or more of the gods as its particular guardian. There were public cults that were devoted to insuring the city against plague, conquest, or want. The religious festival became the occasion for a great assembly of citizens and foreigners.