Thetis

Silver-footed Thetis, or (Ancient Greek: Θέτις) disposer or "placer" (the one who places), was a sea-nymph and the goddess of water. She was the leader of the fifty Nereids, making her a Goddess of water.

In the Trojan War canon (the Epic Cycle)
Thetis is the mother of Achilles, a warrior of Greece who appears in Homer's Iliad. She and Peleus of Phthia had married; after the gods Zeus and Poseidon were attracted to Thetis but then learned from an oracle that her son would be greater than his father, which is the reason they had Peleus marry her instead. Poseidon then chose Thetis' sister Amphitrite to marry instead and she became Queen of the Seas.

A renowned incident at Thetis's and Peleus's wedding was the origin of the Trojan War in the stories by Homer and others.