The Final Descent is a horror novel by Rick Yancey, the fourth and final book in a series that he inaugurated in 2009 with The Monstrumologist (UK title, The Terror Beneath).

[3] The U.S. Library of Congress catalogs The Final Descent as written by William James Henry and edited by Rick Yancey.

[2][4] Fourteen-year-old Will Henry has gone through a lot of horrors with Dr. Warthrop at his side.

Thus in the span of a mere 24 hours, Will's life lies in the balance.

In the depths of Monstrumarium, he has to deal with a monster that is way worse than anything he or Dr. Warthrop could have imagined.