The Red Crystal, official name unknown, is an item found in Marina and Nine's Loric Chests. It is speculated that some of Garde have this item which is paired with the Macrocosm Earth (Glass Orbs), which the other Garde own.
When Marina first opens her chest and sees the object within, she is most intrigued by the glowing crystal which is 'warm and tingly' to touch. As Marina holds this in her hands it begins to glow and grow hotter. However, when she drops it, the compass loses its glow, becoming a faint blue color.
Crayton explains that it uses a Macrocosm to give a location and glows when a Macrocosm is in orbit. He speculates that the Mogadorians have stolen one and can use it to track Marina. It is also thought to be linked to the Glass Orbs as sound was transferred from Marina's compass to Four's orbs on two occasions. While hiding in an abandoned house near the Mogadorian base, Nine attempts to use the device to send a message to the other Garde who may have a way to recieve the message, though this seems futile. Four and Nine are later tracked and captured by the FBI, it is assumed Number Five was involved with this.