The Magician King is the sequel to The Magicians and takes place two years after the events of the first novel. It continues the story of Quentin Coldwater and interweaves it with the story of his high school crush, Julia Wicker], who learned magic outside of the standard school setting and joined him in Fillory as one of the four rulers.
Tired of ruling in Fillory with Eliot Waugh, Margo Hanson, and Julia Wicker, Quentin wants an adventure that will give his life some meaning. He decides to go with Julia to collect taxes from the Outer Island where he learns about a legend involving seven golden keys. The search for one of the keys ends up sending Quentin and Julia back to Earth, and the two must find a way to get back to Fillory.