the Dark Moon has its core working in banishing, transformational or journey work, cuttings and introspective contemplation. The Full Moon and the Dark Moon are both excellent times for scrying in your black mirror, in the embers of the fire, or using whichever form of divination that you see fit.
Mirrors have fascinated humanity since the beginning of time. In fact, there is not a single civilisation on this planet who has not had or currently has an eery tale or magical lore on the mirror. For witches, it is a fantastic scrying tool and to many, nothing really comes close to the art of scrying into a magick mirror.