The ancient Greeks were polytheistic and believed in a pantheon of Gods, some of whom were more powerful than others. Though Zeus was the king of the gods, he was not omnipotent, and other deities controlled specific aspects of nature and human endeavor.
Religion was prevalent in community life in ancient Greece, and ritualistic observance was deemed more important than private individual worship. Theatrical performances, festivals and athletic events all were held in honor of special deities. Different cities had their own protectors. For example, Athens takes its name from the goddess who protected it, Athena, and worshippers built the Parthenon on the Acropolis to honor the virgin goddess.
One aspect of the gods and goddesses ancient Greeks considered dangerous was their human-like behavior. The Greeks believed that the gods were offended if they were slighted by honoring one and not another or if humans boasted of godlike abilities. To appease the gods, priests sacrificed animals. However, because the gods did not need human food, the priests would burn certain entrails ritualistically and then offer the rest of the animal to the people for a feast. Priestesses also appeased the wrath of the gods by pouring libations of various liquids upon flaming altars. According to the ancient Greeks, the gods were anthropomorphic enough to have sex with humans. This gave rise to legends of half-mortal demigods with extraordinary powers. One of the most famous of these demigods was Hercules.