According to Greek myth, Thetis dipped her son [[Achilles]] into the river Styx soon after his birth, an act which rendered him invulnerable to injury, save for a small spot on his heel, covered by Thetis's thumb and forefinger when she held his hand to dip him into the river. | According to Greek myth, Thetis dipped her son [[Achilles]] into the river Styx soon after his birth, an act which rendered him invulnerable to injury, save for a small spot on his heel, covered by Thetis's thumb and forefinger when she held his hand to dip him into the river. |