Sara's necklace.
Sara's necklace (娑蘿の首飾り, Sara no kubikazari, "Sal Tree's necklace") was originally a ordinary necklace, until when Sara merged with yōkai to become an oni hanyō, it contains immense power to petrify things into glossy stone. Apart from the powers she gains after being possessed, it is her most powerful weapon and is depended upon by her at all times.