Distortion of form
This is the easiest way to generate goosebumps. The Pale Man from Pan’s Labyrinth had eyes in his palms. Genius. We leave our comfort zone when we alter the mathematical relationships of the human form. Consider what your monster is meant to do and exaggerate the appropriate parts of the human form, like the Martense clan in HP Lovecraft’s The Lurking Fear, with arms and shoulders grotesquely overdeveloped to serve their subterranean needs.