Attempting to throw the doll away will give you the "Destroy the Undead" quest in the crypt of Betrayal. Basically, this quest asks you to kill 30 undead in CoB.
when examined it says this:(You hold in your hands a very old and sullied doll. You gaze into its eyes.) It gives 2 options when examined put it away or throw it awy. i have had it for a few days going to try the later and see if anything happens.