Sweets as in ice cream and chocolate

Since this one is under mythological creatures, I assume you are not asking about the thickest tendon on the human body, which connects the heel bone to the calf muscle. Mythological Achilles was a warrior, who, according to legend, was dipped in the river Styx (not to be confused with the band Styx, who recorded the hits "Renegade" and "Come Sail Away"), to make him invincible. During the battle of Troy, Achilles was, according to legend, shot in the heel with an arrow dipped in hydra's blood, which poisoned him and caused him to perish. When his mother dipped him in the magical river, she held him by the heel, which left that one part of his body not-invincible (I suppose his mother's hand was then invincible, by the logic of the myth, maybe she was great at cutting vegetables?). Normally a wound to that part of the body would be very painful, but not at all fatal, but, I guess the magical hydra's blood made the wound fatal (not sure why Paris didn't just dip his arrows in the river Styx to make them invincible as well, but nothing in the legend precludes me from believing he didn't at least sing "Domo Oregato, Mr. Roboto" to them).