Thetis, a sea nymph of the Nereids, becomes the center of a dark prophecy revealed by Prometheus that her son will surpass his father, leading Zeus and Poseidon to abandon their pursuit and decree she must wed a mortal. Peleus, descended from Aeacus, lives a troubled life marked by exile and blood-guilt after killing his brother and another by accident, until he is purified and rises to kingship under the guidance of Chiron. Seeking an heir, Peleus seizes Thetis upon the shore and holds her fast as she transforms into fire, rushing water, a lion, and a serpent, enduring each violent change without release until she finally yields, and their union, blessed by the gods, plants the first seeds of the great war that will consume heroes and kings.