Guillermo del Toro is a Mexican filmmaker, author and former special effects makeup artist. Del Toro's movies have always been characterized by a strong connection to fairy tales and horror. All of his life, del Toro was fascinated with monsters, which he considers symbols of power. He relies and is also known for his use of insectile and religious imagery, the themes of Catholicism and celebrating imperfection, underworld and clockwork motifs and practical special effects. Guillermo del Toro's fascination with the horror genre has become one of his trademarks. He navigates this genre using the gothic and multiple intertextual references to literature and visual culture, and emphasizes cruelty, bodily mutilation, the sinister and monstrous characters. The literary part of this thesis analyses the history of the horror movie genre and its monsters as well as mask and creature design in Guillermo del Toro's movies. It also analyzes his body of work from his directoral debut to the newer works. From the first horror movie monsters to the insanely detailed ones. It focuses on the true meaning of being a monster. Inspired by Guillermo del Toro's innovative approach to the modern fairy tale, the creatures that inhabit them and his use of practical effects I have decided to create two masks based on the two main creatures featured in the movie Pan's Labyrinth as the experimental part of my thesis.