Chaos Emeralds (3.5e Equipment)
From D&D Wiki
The Chaos Emeralds are ancient jewels of unlimited power. There are only 7 in existence, each linked to the others. if you have a chaos emerald with you, and it starts glowing, chances are that there is another one nearby. If one is lucky enough to gather all 7, they will become unstoppable. On it's own, a single chaos emerald will allow you to operate special devices, or unlock special powers.