The Bag of Glass Orbs are a set of Loric items that mirrors Lorien's solar system when used. It is not part of the Garde's Inheritence but both Four's Loric Chest and One's Loric Chest, at least, has a set of them.
The Loric Solar System Edit
Henri is finally able to show Number Four its function once he develops his first Legacy (Lumen). In the centre, the size of an orange, is the Sun of Lorien's solar system and it also shows Lorien the way it is now, a barren wasteland. However when Henri blows on it or Four shines his Lumen on the planet, it transforms and it shows what Lorien looked like before the Mogadorian Invasion. (I Am Number Four).
Tracking and Communication Edit
It is later revealed that the glass orbs are somehow linked with the Red Crystals owned by Marina and Nine (at least). Returning to Paradise with Six, Sam and Bernie Kosar to search Sam's back yard, Four looks at the solar system, which transforms into the globe of Earth and he can see Marina's position in Spain as well as hearing her shouting Adelina's name (after opening her chest in the belfry). Crayton tells Marina that the crystal glows when a Macrocosm is in orbit but believes that one has been stolen (The Power of Six).
After leaving the Mogadorian Mountain Base, Four and Nine sift through their Chests and Four removes the glass orbs once again, showing them to Nine. Suddenly, they rearrange into the globe of Earth once again and they can see their own positions, (with their Chests open). They also see a dot in India, signifying Marina's open chest along with the sounds of shouting and chaos (as Six, Marina, Crayton and Ella are attacked), and a dot travelling fast through Brazil, suggesting that Number Five has opened his or her own Chest. (The Rise of Nine).