phenomen a book

Marcelo Moreira, a 15-year-old solitary young man, lived an ordinary life, dealing with school routines and his own problems. But everything changes when he and his entire class are summoned to a medieval kingdom with the mission to defeat a terrible demon. What should have been a heroic opportunity turns into a nightmare when the demon invades the summoning ceremony, kills the responsible mage, and possesses all the students, transforming them into deformed monsters with horns.