The Chain: Shattered: Books 1-4 of The Chain. The Chain

Elliot and Tammy only want to escape their destinies. Blessed with great power but cursed with the impatience of youth, they know there's more to the world than the ridiculous studies they've been exposed to for half their lives. And nothing represents the foolishness of those studies better than the chain necklaces that supposedly magically protect them and bind them to their home. Because who really believes in magic? When they lose the people who had been their only family-a disparate group of mystics known as the Circle-the youngsters must set aside their differences and work together to create a home for those who will one day replace the fallen.
But the Powers-the mysterious sorcerers who destroyed the Circle-won't rest until everyone standing against them is dead. They are unrelenting and merciless, using terrible magic to send powerful ancient spirits such as the Wendigo, cihuateteo, and rakshasi against their enemies. To survive the Powers and their allies' horrifying attacks, Elliot and Tammy must regain the lost knowledge of the Circle before time runs out.
For a suspenseful trip through the supernatural, grab hold of The Chain: Shattered!