Oceanus

Oceanus was the eldest of the twelve Titans, born to Uranus and Gaia, and in Hesiod's Theogony he is the personification of the great river the Greeks imagined encircling the entire flat disk of the inhabited world, the source from which every sea, river, spring and well ultimately flowed. He married his sister Tethys, and Hesiod credits the pair with three thousand sons, the river gods, and three thousand daughters, the Oceanid nymphs, a fertility on a cosmic scale matched by almost no other pairing in Greek genealogy. Unlike most of his fellow Titans, Oceanus took no part in the Titanomachy, the ten year war in which Zeus and the Olympians overthrew Cronus and the older gods. Some later sources explain this as neutrality rather than defeat, and Oceanus is depicted in the Iliad as a figure of primeval calm, once called by Homer the origin of the gods themselves, older and more fundamental than the Olympian order that came after him. He is regularly shown in art as a bearded, sometimes horned figure with crab claw horns rising from his head, often paired visually with Tethys, an image that long outlasted any organized worship of him and carried into Roman decorative art centuries after Greek religion had stopped addressing him directly in cult.

Despite his cosmic scale, Oceanus received essentially no organized cult in ancient Greece. No temple to Oceanus by name is attested, no priesthood served him, and no festival calendar marks a day for his worship the way it does for Zeus, Poseidon or even minor river gods tied to a specific local stream. This is a genuine gap rather than an accident of survival: the Greeks worshipped rivers energetically, since a river's fertility and danger touched daily life directly, but that worship attached to the named river of one's own region, the Ilissos at Athens or the Alpheios at Olympia, each with its own local sacrifices and shrines, rather than to Oceanus as the abstract totality standing behind all of them. Oceanus was too vast and too remote from any single community's landscape to be a patron a city could adopt. What worship existed took the diffuse form of reverence for the sea and for water generally, channeled through Poseidon and through countless local river cults, rather than through any rite addressed to Oceanus by name. Where Oceanus does appear after the classical period, it is chiefly in decorative art, most famously in bath house and villa mosaics across the Greek East, especially around Antioch, where he and Tethys were painted as an ornamental pair rather than approached as objects of prayer.