Monster War is the third book in the Nightmare Academy series by author Dean Lorey following the fictional events in the lives of characters Charlie Benjamin and his friends, Theodore Dagget and Violet Sweet, in their attempt to prevent the remaining Named from traveling back to Earth and summoning The Fifth.
The beginning of the novel takes place with Charlie and friends getting ready for their final exams in the hope of grading and becoming Addys. They are sent by Rex, Tabitha and Pinch to Bungalow C, a place in a rather droopy area owned by Dora [eight years old] and her father Barry. Dora is not old enough to train at the Nightmare Academy yet, and so has not been informed of her ability to portal in Nethercreatures through her Nightmares. Using a Gremlin Attracter, the three friends find and begin to Banish three Gremlins, but not before a Class 2 Darkling from under Dora's bed reaches out and eats them. Still not satisfied, it reaches out to take Theodore, but is only just stopped, saving the skinny boys life. Violet begins closing the portal to the first ring of the Nether she was going to Banish the gremlins with when a Class 4 Netherleaper, Rex calls them 'Dangeroos' captures Violet.
Charlie and Rex save Violet, and begin wondering why a class 4 was found on the first ring of the Nether, when Violet informs them the Netherleaper was taking her to 'the Guardian'. Hearing this, Rex, Tabitha, Pinch, Charlie, Theodore and Violet portal to the Nightmare Division and tell the Headmaster. She explains that remaining two Named, Slagguron and Tyrannus, was trying to poison the Guardian, the strange creature whose aura protects the Nightmare Academy. The touch of a child is enough to kill it.
Suddenly, they are called to the Nightmare Division by the Director, Drake. He informs the Headmaster, Rex, Tabitha,Pinch and Charlie and his friends that he remembers what they did to him in the first book. He had regained his memories. They take him back to the Hags of the Void,where they form a truce not to steal his memories in return for him being civilised towards Charlie and friends.
Outside a window, they hear the screeching voice of Tyrannus saying they have killed the Guardian.The Guardian guards a place called the Anomaly, a weak spot between the Nether and Earth which Slagguron and Tyrannus wish to escape through. Brook takes Charlie and friends into the Anomaly to check on the Guardian and the Headmaster who had already left. They realize the Guardian has been poisoned, and that the only cure is the milk from a female Hydra. The only problem is that there is only one in existence. The Headmaster also informs that they are qualified Addys and are allowed to upgrade their weapons. Charlie chooses another rapier and Violet chooses a double sided axe.
Charlie retrieves the Hydra's milk and takes it back to the Nightmare Academy. In a fit of greed, Pinch without warning drinks some of the content of the milk. He turns back into a teenager and receives all his powers back. Pinch portals them to the 5th Ring, as close as they can get to the Anomaly, and find it is swarming with monsters. The group, finding a frightened boy, rescue him and take him back to the Academy without delay. They were tricked. The boy was Slagguron. Slagguron is a Changling. Changling can change forms for a short time.
Charlie revives the Guardian but fails in stopping Tyrannus from coming through to Earth. They decide on a new plan. Charlie takes the Guardian to the Named's new base, disabling all the Nethercreatures who stand in their way. But in an act of cruelty, Director Drake kills the Guardian. Meanwhile, Pinch killed Verminion, but is shunned away as they blame him for the Guardians death. In a fit of rage and sorrow, Pinch takes Verminion's place and helps the other Named summon the Fifth.
The Fifth is a giant female Nethercreature. She kills all of the Named, but leaves Pinch alive. He joins the enemy. Charlie and friends narrowly escape with their lives, but they have failed. The Fifth is free. The War of the Nether has truly begun. This book was before the book 3 in the Nightmare Academy series, Monster Revenge. Monster Revenge is also known in the U.S.A as Monster War.