The first ancient reference of religious ceremonies for them is found in the Homeric Hymn to Hermes. The Greek cult of the Twelve Olympians can be traced to the 6th century BC Athens and probably has no precedent in the Mycenaean period. The altar to the Twelve Olympians at Athens is usually dated to the archonship of the younger Pesistratos, in 522/521 BC. The concept of the "Twelve Gods" is older than any of our Greek or Roman sources, and is likely of Anatolian origin. There seems to have been a great deal of fluidity when it came to who was counted among their number in antiquity.
The gods are indistinguishable from humans in appearance, though some look radically different. Gods, in their natural state, are above-average size, but some, like Hephaestus, Hades, and Ares are and can become very large, though not on the scale of elemental Titans. The Olympians also have the ability to increase/decrease their size considerably, but this is usually only for combat. Gods vary greatly in forms and power, more so than the Titans, who are all similar in that they're enormous beings embodying the elements.
Also noteworthy is the fact that when a God dies, a devastating event occurs that is sometimes called a plague. The plague is based on what the god personifies like great flood waters (Poseidon), deadly swarms of flies (Hermes), and the souls of the dead escaping (Hades). The weaker gods, like Ceryx, however, die without any major consequences, as do Hephaestus and Athena. However, it is possible that these events are not major enough to warrant much attention.
The classical scheme of the Twelve Olympians (the Canonical Twelve of art and poetry) comprises the following gods:
- Zeus: The God of the sky, thunder, and lightning. The ruler and father of Olympus and King of the Gods.
- Asclepius: The God of medicine and healing.
- Aphrodite: The Goddess of love, beauty and desire.
- Ares: The God of War.
- Artemis: the Goddess of the hunt and virginity.
- Athena: the goddess of Wisdom, Strategic Warfare and Heroism.
- Apollo: the God of Light and Music.
- Demeter: Goddess of agriculture and mother to Persephone.
- Eos: the Goddess of the Dawn and sister to Helios.
- Hades: God of the Underworld and ruler of the Dead.
- Helios: God of the Sun.
- Hera: The Goddess of Women and Marriage, the sister-wife of Zeus, and the Queen of the Gods.
- Hermes: the messenger God of Olympus and God of travellers, speed, commerce and thievery.
- Hephaestus: the Smith God of Olympus, and God of Fire.
- Morpheus: the God of Dreams.
- Persephone: the Goddess of Fertility, Innocence, and the Queen of the Underworld.
- Poseidon: the God of the Seas.
- Thanatos: God of Death.
- Amphitrite: A sea Goddess and consort of Poseidon.
- Ceryx: The son of Hermes and a messenger God.
- Boreas: The God of the North Wind.
- Eurus: The God of the East Wind.
- Notus: The God of the South Wind.
- Zephyrus: The God of the West Wind.
- Sisters of Fate: The three sisters Atropos, Lahkesis, and Clotho, control time and the fate of all.