The Locket of Vor hosts a spirit that was imprisoned inside of it. The spirit knows where to find the Wicked Nine, nine magical objects that belong to history's most devious villains. Because these objects will unleash unspeakable power when brought together, the Protectors locked it inside a safe in the Terrible Tower in their castle on the Mystic Isles. They sealed it in with a Crystal Lock made by the Crystalmasters on the Isle of Crystals.
It first appears in "The Mystic Isles: The Falcon's Eye". After Prisma's capture, she was locked into a cell next to where the Locket's safe is. This proves to be a mistake: Prisma recognizes the Locket for what it is and sees it as the key to her freedom. After a strangling named Twitch shows up, Prisma tells him how to get the Locket for her since she knows about Crystal Locks due to the fact she and her sister Azurine made them all the time. After Twitch gets it, Prisma opens the Locket and frees the spirit. The spirit tells Prisma about the Wicked Nine and how, if the objects are brought to her, she will get her powers back. Twitch goes to get the first one for Prisma. When he returns with a Necissi-Key, Prisma breaks out and goes to get them herself.
The Locket's spirit has a similar appearance to the spirit of the Evil Queen's Magic Mirror.