Goblin Magic, 17

The people of Wrenly have always believed that goblins are dangerous creatures who were stripped of their magical powers by wizards after the Goblin Battles; and when Prince Lucas and Clara follow a young goblin, Zark, who has come from the wizard Grom, they find themselves captured by the goblin leader Golart, who has taken over Hobsgrove--but Grom has a plan, and it requires that the children put their trust in Zark.