Keepers of the Vault: Melody and Myth by Marty Chan

In this action-packed sequel to Fire and Glass, Kristina and Dylan team up with Dr. Grimoire to thwart the plans of a rogue former apprentice to steal one of the vault’s most valuable possessions – the legendary Golden Fleece. But she has already managed to get her hands on a few artefacts with some dangerous powers – including a magical music box that can ensnare anyone who hears it.