The nymph mother of Achilles
Thetis was a sea nymph (Nereid) who was the mother of Achilles with her mortal Peleus husband. Her father was the sea god Nereus and her mother was Doris and she was granddaughter of the Titan Oceanus and his wife Titheia..
Peleus had conquered Thetis by holding on to her while she was taking on different forms – everything from animals to fire. According to another version the gods had ordered her to marry a mortal.
Both Zeus and Poseidon had wanted to marry her, but when Themis prophesied that her son would be stronger than them both, they considered it wiser to give her to a mortal. It was at their wedding the Trojan war became an issue. They had invited all the gods except the goddess of arguments and misunderstandings, Eris, and she took her revenge by throwing a golden apple with the inscription “to the most beautiful” into the party, resulting in the argument between Hera, Athena and Aphrodite and she became the essential reason for unleashing the Trojan War
Thetis, according to the myth, gave birth to a son, Achilles, whom he attempted unsuccessfully to make immortal, she allegedly baptise the child in the river of Stinx, holding it from the heel. All the points of his body that the river touched, became invulnerable. But the heel was dry and so Achilles had his vulnerability as a symbol of his mortality.
By defining Thetis through a selective presentation of her myth, Homer’s Iliad gives emphasis to her properties as a mother-nanny and a protector.This aspect of Thetis, the mother care and protective power as it is adapted to the Iliad, highlights one of the central ideas of the epic, the weakness even of the greatest hero. A half god such as Achilles can not avoid death.
The Secret of Thetis is inevitably linked to the survival of Zeus: its governance and its future are trapped in her fatal power. Although the danger against Zeus from Hera, Athena and Poseidon was prevented by Thetis,she is the same that presents itself as the greatest challenge to its superiority, according to the legends.