Amulet of the Bloody Luck

This amulet was created by paranoid mage who feared the unknown more than pain itself. He could withstand spells, traps and other effects by pure will-power and a heavy nosebleeds. His life ended in a very long battle. No spell could ever touch him, but he died anyway...

When you wear the amulet and fail a saving throw, you can decide to throw another d20 and use that at the cost one point of exhaustion or 4d10 necrotic damage.
Alternatively you can add a bonus to your saving throw for 1d10 necrotic damage per point.

Notes: Buff, Jewelry