Thetis

The silver-footed, fair-haired Thetis, who plays an important part in the mythology of Greece, was the daughter of Nereus, or, as some assert, of Poseidon.

Her grace and beauty were so remarkable that Zeus and Poseidon both sought an alliance with her; but, as it had been foretold that a son of hers would gain supremacy over his father, they relinquished their intentions, and she became the wife of Peleus, son of Æacus. Like Proteus, Thetis possessed the power of transforming herself into a variety of different shapes, and when wooed by Peleus she exerted this power in order to elude him. But, knowing that persistence would eventually succeed, he held her fast until she assumed her true form.

Their nuptials were celebrated with the utmost pomp and magnificence, and were honoured by the presence of all the gods and goddesses, with the exception of Eris. How the goddess of discord resented her exclusion from the marriage festivities has already been shown.

Thetis ever retained great influence over the mighty lord of heaven, which, as we shall see hereafter, she used in favour of her renowned son, Achilles, in the Trojan War. When Halcyone plunged into the sea in despair after the shipwreck and death of her husband King Ceyx, Thetis transformed both husband and wife into the birds called kingfishers (halcyones), which, with the tender affection which characterized the unfortunate couple, always fly in pairs.

The idea of the ancients was that these birds brought forth their young in nests, which float on the surface of the sea in calm weather, before and after the shortest day, when Thetis was said to keep the waters smooth and tranquil for their especial benefit; hence the term "halcyon-days," which signifies a period of rest and untroubled felicity.

From: Berens, E.M. The Myths and Legends of Ancient Greece and Rome. New York: Maynard, Merril, & Co., 1880. Text in the public domain.