Demeter in the context of "Protesilaus"

Religious practices in ancient Greece encompassed a collection of beliefs, rituals, and mythology, in the form of both popular public religion and cult practices. The application of the modern concept of "religion" to ancient cultures has been questioned as anachronistic. The ancient Greeks did not have a word for 'religion' in the modern sense. Likewise, no Greek writer is known to have classified either the gods or the cult practices into separate 'religions'. Instead, for example, Herodotus speaks of the Hellenes as having "common shrines of the gods and sacrifices, and the same kinds of customs".

Most ancient Greeks recognized the twelve major Olympian gods and goddesses—Zeus, Hera, Poseidon, Demeter, Athena, Ares, Aphrodite, Apollo, Artemis, Hephaestus, Hermes, and either Hestia or Dionysus—although philosophies such as Stoicism and some forms of Platonism used language that seems to assume a single transcendent deity. The worship of these deities, and several others, was found across the Greek world, though they often have different epithets that distinguished aspects of the deity, and often reflect the absorption of other local deities into the pan-Hellenic scheme.

In ancient Greece, deities were regarded as immortal, anthropomorphic, and powerful. They were conceived of as individual persons, rather than abstract concepts or notions, and were described as being similar to humans in appearance, albeit larger and more beautiful. The emotions and actions of deities were largely the same as those of humans; they frequently engaged in sexual activity, and were jealous and amoral. Deities were considered far more knowledgeable than humans, and it was believed that they conversed in a language of their own. Their immortality, the defining marker of their godhood, meant that they ceased aging after growing to a certain point. In place of blood, their veins flowed with ichor, a substance which was a product of their diet, and conferred upon them their immortality. Divine power allowed the gods to intervene in mortal affairs in various ways: they could cause natural events such as rain, wind, the growing of crops, or epidemics, and were able to dictate the outcomes of complex human events, such as battles or political situations.

As ancient Greek religion was polytheistic, a multiplicity of gods were venerated by the same groups and individuals. The identity of a deity was demarcated primarily by their name, which could be accompanied by an epithet (a title or surname); religious epithets could refer to specific functions of a god, to connections with other deities, or to a divinity's local forms. The Greeks honoured the gods by means of worship, as they believed deities were capable of bringing to their lives positive outcomes outside their own control. Greek cult, or religious practice, consisted of activities such sacrifices, prayers, libations, festivals, and the building of temples. By the 8th century BC, most deities were honoured in sanctuaries (temenē), sacred areas which often included a temple and dining room, and were typically dedicated to a single deity. Aspects of a god's cult such as the kinds of sacrifices made to them and the placement of their sanctuaries contributed to the distinct conception worshippers had of them.

Poseidon (/pəˈsaɪdən, pɒ-, poʊ-/; Ancient Greek: Ποσειδῶν, romanised: Poseidôn) is one of the twelve Olympians in ancient Greek religion and mythology, presiding over the sea, storms, earthquakes and horses. He was the protector of seafarers and the guardian of many Hellenic cities and colonies. In pre-Olympian Bronze Age Greece, Poseidon was venerated as a chief deity at Pylos and Thebes, with the cult title "earth shaker"; in the myths of isolated Arcadia, he is related to Demeter and Persephone and was venerated as a horse, and as a god of the waters. Poseidon maintained both associations among most Greeks: he was regarded as the tamer or father of horses, who, with a strike of his trident, created springs (the terms for horses and springs are related in the Greek language). His Roman equivalent is Neptune.

Homer and Hesiod suggest that Poseidon became lord of the sea when, following the overthrow of his father Cronus, the world was divided by lot among Cronus' three sons; Zeus was given the sky, Hades the underworld, and Poseidon the sea, with the Earth and Mount Olympus belonging to all three. In Plato's Timaeus and Critias, the legendary island of Atlantis was Poseidon's domain. In Homer's Iliad, Poseidon supports the Greeks against the Trojans during the Trojan War. In the Odyssey, during the sea-voyage from Troy back home to Ithaca, the Greek hero Odysseus provokes Poseidon's fury by blinding his son, the Cyclops Polyphemus, resulting in Poseidon punishing him with storms, causing the complete loss of his ship and numerous of his companions, and delaying his return by ten years.

In ancient Greek religion and mythology, the twelve Olympians are the major deities of the Greek pantheon, commonly considered to be Zeus, Poseidon, Hera, Demeter, Aphrodite, Athena, Artemis, Apollo, Ares, Hephaestus, Hermes, and either Hestia or Dionysus. They were called Olympians because, according to tradition, they resided on Mount Olympus.

Besides the twelve Olympians, there were many other cultic groupings of twelve gods.

In ancient Greek religion and myth, Dionysus (/daɪ.əˈnaɪ.səs/ ; Ancient Greek: Διόνυσος Diónysos) is the god of wine-making, orchards and fruit, vegetation, fertility, festivity, insanity, ritual madness, religious ecstasy, and theatre. He was also known as Bacchus (/ˈbækəs/ or /ˈbɑːkəs/; Ancient Greek: Βάκχος Bacchos) by the Greeks (a name later adopted by the Romans) for a frenzy he is said to induce called baccheia. His wine, music, and ecstatic dance were considered to free his followers from self-conscious fear and care, and subvert the oppressive restraints of the powerful. His thyrsus, a fennel-stem sceptre, sometimes wound with ivy and dripping with honey, is both a beneficent wand and a weapon used to destroy those who oppose his cult and the freedoms he represents. Those who partake of his mysteries are believed to become possessed and empowered by the god himself.

His origins are uncertain, and his cults took many forms; some are described by ancient sources as Thracian, others as Greek. In Orphism, he was variously a son of Zeus and Persephone; a chthonic or underworld aspect of Zeus; or the twice-born son of Zeus and the mortal Semele. The Eleusinian Mysteries identify him with Iacchus, the son or husband of Demeter. Most accounts say he was born in Thrace, traveled abroad, and arrived in Greece as a foreigner. His attribute of "foreignness" as an arriving outsider-god may be inherent and essential to his cults, as he is a god of epiphany, sometimes called "the god who comes".

In ancient Greek mythology and religion, Persephone (/pərˈsɛfəniː/ pər-SEF-ə-nee; Greek: Περσεφόνη, romanized: Persephónē, classical pronunciation: [per.se.pʰó.nɛː]), also called Kore (/ˈkɔːriː/ KOR-ee; Greek: Κόρη, romanized: Kórē, lit. 'the maiden') or Cora, is the daughter of Zeus and Demeter. She became the queen of the underworld after her abduction by her uncle Hades, the king of the underworld, who would later take her into marriage. The myth of her abduction, her sojourn in the underworld, and her cyclical return to the surface represents her functions as the embodiment of spring and the personification of vegetation, especially grain crops, which disappear into the earth when sown, sprout from the earth in spring, and are harvested when fully grown.

In Classical Greek art, Persephone is invariably portrayed robed, often carrying a sheaf of grain. She may appear as a mystical divinity with a sceptre and a little box, but she was mostly represented in the process of being carried off by Hades.

Serapis or Sarapis is a Graeco-Egyptian god. A syncretic deity derived from the worship of the Egyptian Osiris and Apis, Serapis was extensively popularized in the third century BC on the orders of Greek Pharaoh Ptolemy I Soter, as a means to unify the Greek and Egyptian subjects of the Ptolemaic Kingdom.

The cultus of Serapis was spread as a matter of deliberate policy by subsequent Ptolemaic kings. Serapis continued to increase in popularity during the Roman Empire, often replacing Osiris as the consort of Isis in temples outside Egypt.Alongside his Egyptian roots he gained attributes from other deities, such as chthonic powers linked to the Greek Hades and Demeter, and benevolence derived from associations with Dionysus.