In Trojan War mythology, Achilles was famously vulnerable in his heel.
Achilles was the greatest Greek warrior in many accounts of the war against Troy. Later traditions say that his mother, the sea goddess Thetis, tried to make him invulnerable by dipping him in the River Styx. She held him by one heel, leaving that spot untouched by the river’s protective power.
The Iliad itself does not tell this story or describe Achilles as invulnerable. Homer’s poem instead presents Achilles as a powerful but mortal fighter, and it ends before his death. The heel story became prominent in later Greek and Roman traditions.
The expression “Achilles’ heel” now means a person’s particular weakness. In later retellings, Paris kills Achilles by shooting an arrow into his heel, sometimes with Apollo’s help. Different ancient and modern versions vary on exactly how the fatal shot occurred.