Magic communication device
A person using this crystal concentrates on another person, who also must have a pre-linked crystal, to open telepathic communication. When ‘calling’ the other person, the receiver knows who is trying to contact them and can accept or deny the connection.
This item only works when in direct contact with the skin, and as such, many owners may attach it to a chain, an article of clothing, or decorative jewelry to name a few examples.
These crystals were given to the players and Jet to help them remain in contact even though, for safety, they were all required to be separated. A member (possibly more) of the school faculty also has a crystal to keep tabs on the former students.