Imaginary monsters are creatures that exist only in the imagination, often featured in fantasy literature and films. The term 'CHIMERA' (7 letters) refers to a creature from Greek mythology composed of parts from multiple animals, such as a lion, goat, and snake. The term 'BUGABOO' (7 letters) is a slang term for an imaginary monster used to frighten children. Finally, the term 'Orc' (3 letters) is a monstrous humanoid creature from Tolkien's Middle-earth universe.