Also covered by enchantments to completely mask its true nature, a necklace of strangulation can be discovered only when placed around a character's neck. 

The necklace' immediately constricts and cannot be removed short of an alter reality, limited wish or wish spell. 

The wearer will suffer 6 hit points of strangulation damage per round until the character is dead and the necklace' remains clasped until the character is a dry skeleton.