A Sight Crystal is a reflective piece in the shape of a gem which allows a person to communicate through great distances with another person as well as see the person on the other end. Sight Crystals were mainly used among the Clergy of Mardük in various ages. After the fall of Yamato to demons in the Cataclysm, demons began using the remaining Sight Crystals for long distance communication between demon lords and their agents who were spying on the Land of the Living. Gem Communicators are derived from Sight Crystals but have inferior range and only provide the means for aural communication.