Thetis was another sea nymph love of Zeus. This affair was exceedingly short term, as there was a prophesy that she would bear a son greater than his father. As we all know, Zeus would go to great lengths to avoid being overthrown, so he handed his lover over to Peleus, the king of Thessaly.

Her child was Achilles. In order to safe-guard him, she took her baby to the river Styx and dipped him into the waters. This made him invulnerable, all except the heel which she had held him by (I never understood why she didn't switch hands to let the heel get covered too), hence the term "Achilles heel". Thetis wanted the best education for her son, so she had the centaur Chiron educate him. Obviously Chiron could not beat out the stupidity of youth, because the Fates made an offer to young Achilles; Have a long life of heath and happiness, but be unknown to the world, or have a short life but be immortalized with fame. He choose to die young.

Little else is known about Thetis, but there are many stories about her son.

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