Achilles was the sun a peleus. peleus was a mortal and a king it was said that he was a powerful soldier as well. He had a mother named thetis she was a nereid, a nereid is one out of the 50 daughters of nereus a sea nymph. Nereid wanted achilles to be an immortal so she did stuff like put him over a fire every night or dress his wounds with ambrosial because she knew that his fate was to die in a war [the trojan war] she did all of that because immortals don't die when he was 9 his dad dressed him up as a girl and sent him to the island in the aegean sea called skyros. You can't change fate so he soon left skyros and joined the greek army nereid his mother tried one more time to save him so she asked hephaestus the god of blacksmiths to