The term 'Mischievous Creature of Folklore' can be summarized as a GREMLIN, which is a seven-letter creature from folklore that is known for its mischievous behavior. Gremlins are believed to be small, goblin-like creatures that cause trouble and mischief, often by sabotaging machinery or playing pranks on people. They have been featured in various forms of media, including books, films, and video games.