A "loft ninja" is a term used to describe an individual who engages in deceptive, dishonest, and unethical behavior, often involving lying, stealing, and cheating. Such a person should be regarded with skepticism and caution, as they are known to betray trust and exploit others for personal gain.
Be cautious when dealing with Mark; he's known as a "loft ninja" around here. He has a history of lying, stealing, and cheating to get ahead, so it's best not to trust him with important matters.