Mnemosyne — Classical Greek Myth Library

Thetis the Nereid was desired by Zeus (and, in some tellings, Poseidon), but Themis (or Prometheus) warned that her son would be mightier than his father. The gods therefore compelled her to marry a mortal. Peleus son of Aeacus, purified and settled in Phthia, was chosen. Chiron advised him how to win her: seize Thetis as she slept on the shore (Sepias or a Thessalian coast) and hold fast while she changed shape. She became fire, water, wind, a tree, a tiger, a lion, a cuttlefish—Pindar and Apollodorus vary the list—but Peleus did not let go. Exhausted, she consented to be his wife. The wedding feast on Pelion, with gods bringing gifts and Eris casting the apple of discord, belongs to the Trojan cycle’s opening; this entry covers only the prior struggle: divine policy that a Nereid’s child must not overthrow Olympus, and the hero’s wrestling endurance that wins Achilles’ mother. The marriage is thus both honor and constraint—Thetis forever resentful of mortality forced upon her bed, Peleus briefly the gods’ favorite son-in-law.