Crystalomancy, also known as Scrying, is the practice of looking into a reflective surface in the hope of detecting significant messages or visions.
The city is full of surfaces to scry, especially on rainy days: gaze into your own reflection in the train or bus windows, or look through your dorm window before going to sleep. If you
improve your ability to focus every reflective surface is valid, even puddles on the ground.
Grey magic is magic that is not performed for specifically beneficial reasons, but is also not focused towards completely hostile practices. It is seen as falling in a continuum between White and Black Magic.