What is the relationship between the moon stone and vampires from The vampire diaries?

The moon stone relates to vampires because it was made by Katherine to be a curse. With the moon stone, and a dople gamer, a witch, and a vampire, you can do a spell that will destroy the curse. Katherina turned Carline, and was going to use bonnie to break the spell, and Elena is the Dopple gamer.

Tune into the Vampire Diaries on December, 2nd and watch "The Sacrifice"