Themis was born among the twelve Titans, the first generation of gods sired by Uranus, the starry Sky, upon Gaia, the broad-breasted Earth. Her name means that which is laid down, the established rule, and she was exactly that in divine form: not the law of any city or king, but the deep order underneath all laws, the way things must be if the world is to hold together. When her brother Cronus struck down their father with a flint sickle, and later when Zeus, the son of Cronus, fought the ten-year Titanomachy, the war between the old Titans and the young Olympian gods, Themis took no part in the violence. Order does not need a spear. When the fighting ended and Zeus divided the cosmos, Themis kept her place, because no king, not even the king of the gods, can rule a universe that has no law beneath it.

Before the Olympians, prophecy belonged to the Earth herself, and the first oracle in the world stood at Delphi, a cleft in the rocks on the slopes of Mount Parnassus in central Greece, where vapours rose and the future could be heard. Gaia held that oracle first, and Themis, her daughter, held it second, speaking the will of the Earth to those who came to ask. In time Themis passed the shrine to her sister Titaness Phoebe, and Phoebe gave it as a birthday gift to her grandson Apollo, the radiant god of prophecy, music and the sun, whose priestess would make Delphi the most famous oracle in the ancient world. But the Greeks never forgot the line of succession. The tragic poet Aeschylus opened his play about Orestes, the prince who killed his own mother to avenge his father, with the Pythia, the priestess of Delphi, reciting that very genealogy of prophetesses, and Themis's name stands in it before Apollo's, the older law behind the younger god.

After Zeus won his throne, he took Themis as his second wife, and their marriage was less a romance than a constitution. She bore him the Horae, the Hours or Seasons: Eunomia, Good Order, Dike, Justice, and Eirene, Peace, the three guardians of the golden year. She bore him also the Moirai, the three Fates, darker daughters than any bride should bear: Clotho, who spins the thread of life, Lachesis, who measures it out, and Atropos, who cannot be turned aside and who cuts it with her shears. Even Zeus is subject to the Fates, which means that the king of the gods is bound by the children of his own wife. In Homer's Iliad, the epic of the Trojan War, it is Themis whom Zeus sends to summon the gods to their assembly, and in the lost epic of the war's beginnings it was Zeus and Themis together who planned the whole catastrophe, resolving to thin the swarming nations of mankind with a decade of war at Troy, because the Earth herself had complained of the weight of so many mortal mouths.

Themis's greatest prophecy saved the throne of heaven. The sea nymph Thetis, a silver-footed goddess of the waves, was courted by both Zeus and his brother Poseidon, the earth-shaking god of the sea, and marriage to either might have changed the world. But Themis stood in the midst of the assembled gods and spoke what she knew: the son of Thetis was destined to be mightier than his father. Zeus had overthrown his own father Cronus, who had overthrown his father Uranus, and he understood at once. The gods withdrew their suits, and Thetis was married instead to Peleus, a mortal man, so that her world-shaking son would be mortal too. He was Achilles, the greatest warrior of the Trojan War, mightier than his father, just as Themis had foreseen, but no threat to heaven. In another telling, it was from his mother Themis, whom the poet Aeschylus identifies with the many-named Earth, that the rebel Titan Prometheus learned the same secret, and his refusal to reveal it to Zeus was the real cause of his centuries of torment upon the crag.

The last great tale of Themis belongs to the end of the world. When Zeus drowned the corrupt race of bronze in a Great Flood that covered the mountains, only two mortals survived in a wooden chest: Deucalion, the son of Prometheus, and his wife Pyrrha, the daughter of Epimetheus, the foolish Titan who had accepted Pandora. For nine days and nights they drifted, until their vessel grounded on the peak of Mount Parnassus. Climbing down into a world of mud and silence, the two survivors found the one shrine the waters had spared, the oracle of Themis, and veiling their heads they begged the goddess to tell them how mankind might live again. The voice answered: cast behind you the bones of your great mother. Deucalion understood the riddle: the great mother is the Earth, and her bones are the stones. He and Pyrrha threw stones over their shoulders, and where they fell, men and women rose up from the ground, a new race born of the Earth's own body. The Roman poet Ovid told the tale in his Metamorphoses, the great Latin epic of transformations, and it is Themis who gives mankind its second beginning. Her memory has never left the law: her daughter Dike became the Roman Justitia, and the blindfolded woman with the scales who stands above courtrooms and parliaments across the modern world is the child of Themis in all but name.