The Achilles Heel only may be made if you are dipped/jump in a river with sticks (it's a budget River Styx). If your strength is above 17, you gain this trait otherwise you burn up and your character dies unless it is fully immune to radiant damage. When you gain this trait, you choose whether it is on the front or the back.

The Achilles Heel allows you to tank every single hit tanking no damage, unless they roll 2 d20s and if they are facing the side that your Achilles Heel is on. If you get above 39, it insta-kills if it is used with a weapon or a spell, an unarmed blow does the normal damage. A person with knowledge of your Achilles Heel's position has advantage on this dice roll.