The Magisterium Series is intended to be a 5-book series for young adults. It is a fantasy series co-authored by Holly Black and Cassandra Clare. It is their first collaboration. The series was acquired by Scholastic in April 2012. The first book, The Iron Trial, was published in September 2014, and hit #3 on the New York Times Middle Grade Bestseller List. The books are set in an underground school where mages train apprentices to control the elements. The books are illustrated by Scott Fischer.