The Locked Tomb Series is a science fiction and fantasy book series written by Tamsyn Muir. It begins with the novel Gideon the Ninth, which follows Gideon Nav, a necromancer's servant, as she becomes embroiled in a deadly competition among necromancers. The series is known for its unique blend of gothic elements, humor, and intricate world-building. The second book, Harrow the Ninth, continues the story, focusing on Harrowhark Nonagesimus, a powerful necromancer. The series explores themes of loyalty, identity, and the complexities of relationships, all set against a backdrop of political intrigue and necromantic magic. The third installment, Nona the Ninth, further expands the universe and its characters.