Zweischneid said:Maybe you've read a different version than I did, but in my book Achilles was indeed invulnverable due to being dipped into the River Styx by his Mother Thetis as a sacrifice to Poseidon, and only vulnerable only at the heel where his mother gripped him.
However, that is not in the Iliad. It's something introduced by later versions of the story, in particular Ovid's Metamorphoses, I believe.