The Moonstone is a translucent, milky-colored and flat ovoid gemstone that is approximately the size of the hockey puck; resembling milk quartz moreso than true moonstone. The stone plays a key role in the central plot arc of the second season and is sought after by several of the seasons antagonists. Later it was known that the stone is the magical focus of the The Sun & The Moon Curse placed on vampires and werewolves.
The moonstone was originally used some time in the 15th century by The Original Witch as the focus of a curse laid on both vampires and werewolves. The effects of the curse made vampires vulnerable to the sun and tied the werewolves transformation to the full moon. As a key part of their curse, the stone is considered immensely valuable to both vampires and werewolves who know of its history. With the correct combination of blood from a werewolf, a vampire, the stone and a witch could reverse the curse. It is believed that the owner of the moonstone could control how the curse was removed. For example, a werewolf could leave the vampires curse of the sun in place while removing the werewolves curse of the moon.
- It is unknown what happened to the Moonstone after the sacrifice but it can be assumed that it was destroyed.