Necklace of Strangulation

This beautiful necklace appears to be a magical item such as a necklace of fireballs or a Pendant of the Occult. When invested, it magically locks in place, suspiciously tightly, and fuses to you. When you enter a situation of extreme stress (as determined by the GM), the necklace tightens around your neck, suffocating you and dealing 30 bludgeoning damage to you at the end of each of your turns. Once per round, you can spend a single action to attempt a DC 34 Athletics check or Fortitude save; success means you don't take the damage on your current turn, but you continue suffocating. The necklace loosens after you've been dead for a month.