Thetis is one of the fifty daughters of Nereus and Doris, who were called the Daughters of Nereus. Thetis was given to Peleus, who was a mortal, for his undying devotion to the gods on Olympus. Thetis and Peleus had a magnificent son, Achilles. Achilles had a choice, he could either die happy but forgotten, or he could die in the Trojan War and be remembered as a hero forever.

Thetis protected her son in battle by providing him with armour made from the smiths of the gods. But during the Trojan War, Achilles was angry with Agamemnon, and he refused to fight. So instead, he gave his armour to his friend Patroklos. Patroklos was killed as he pressed the attacks to the walls of IIion. The most brutal fighting of the war was for the armour of Achilles and the body of Patroklos. Thetis led a procession of her sisters up from the depths to cry openly and to cast a mist over the body of Patroklos.