Withered Elf Heart

The shrunken heart of a long dead elven
enchantress hung on a strip of black leather.
It feeds on its wearers life force to keep them sane.
when making a saving throw against an effect
that wound charm, possess or otherwise compel
the wearer to act against their will, the wearer
spends a hit die. add the result to the saving
throw, and take an equal amount of necrotic
damage. This happens whether the wearer wants
it or not. If the wearer is out of hit die, make a
saving throw as normal.