From Pathfinder Bestiary, which isn't enabled.

Heartstone

ITEM 9

Price 600 gp

Usage worn

Bulk —

This gemstone grants its wearer a +2 item bonus to saving throws.

Each heartstone is powered by the spirit of a specific night hag. If it's separated from her for 24 hours (or she's been dead for 24 hours), it becomes a nonmagical gemstone. A heartstone allows the hag to use additional occult innate spells: Ethereal Jaunt (9th level) and Seize Soul at will, and Shadow Blast twice per day.

Activate command

Requirements You must be touching the heartstone.

Effect The heartstone attempts to counteract one disease affecting you (counteract rank 5, counteract modifier +18).

Craft Requirements You must be a night hag.

Pathfinder BestiaryOGL