Sunstone pendants have a power over the people who wear them, as in the case of the two Tiefling sisters found in whalespell. Once under the control of the pendants a person has no recollection of the events that transpire during your time under its control.
As far as we know each pendant will adhere to the wearer chest, only being removed when the controlling sunstone orb has been destroyed. One such orb was recovered from a mage encountered just outside whalespell in a rundown windmill. 