Ariadne also notices that her crystal pendant , the one given to her by the girl , Serena , is vibrating and glowing slightly . The girls told her that the crystal was " sensitive to spirits " . As the party ascended the stairs , the pendant only grew brighter , indicating a high level of spirit activity . At the top of the stairs they found what remained of a once - lavishly appointed bedchamber . 
Question: What's a possible reason the crystal pendant is vibrating and glowing ?
Because it has magical properties .