Graveheart's Data Crystal.
Data Crystals are used to store many forms of electronic data including personal files, access codes and security codes. Heads of State in the Alliance have Data Crystals containing security and access codes to the Alliance's defenses.
Graveheart was given a blue Data Crystal with the Alliance's defense codes early on, which he wore as a necklace throughout the series. In Girls Night Out, Tekla gave Jade a similar green Data Crystal, which she gave to Lord Mantel in return for lending his Battle Moons to the assault on Planet Remora. Mantel used it to immobilize and take over the Alliance, which led to his death at Blokk's hands. Just before he was killed, he smashed the green crystal to prevent Blokk from getting it.