The black scrying mirror, or magick mirror, is a powerful psychic tool. It can bring the user hidden knowledge and clairvoyant ability and can act as a portal to other planes of existence. History shows its use in many of the traditional mystery schools and oracular temples. Today the serious student of magickal arts can rediscover the ancient rites of the magick mirror, for these techniques are again coming to light.
Scrying can be defined as the mantic art of gazing into or upon a crystal or dark mirror, allowing the physical eyes to relax, thus letting the inner psychic eyes begin to open and receive desired visions or information. The use of the black mirror is one of the best methods of achieving the state of mind required for entering trance and for scrying work. It not only acts as a focal point for visualization but can become a doorway into the astral plane. It allows communication with higher realms and the subconscious and access to Akashic records. The traditional crystal ball is also a wonderful tool, but it is more difficult to scry with and is extremely expensive. The mirror is a more efficient way to begin to learn to scry and journey in other realms.
Article Source [wicca.com]