Moonstones

The Moonstones are old, very old artifacts. It is unknown from where they actually come, but they are bound to the phases of Britannia's twin Moons Trammel and Felucca. There exist eight of them, each showing a different moon phase. Where they are buried into the ground, a Blue Moongate appears at night, linked to the phase the Moonstone represents. Of course each Moonstone can be excavated and planted elsewhere.

The Moonstones were first found in Ultima V at the sites of the Moongates, where they could be excavated and re-buried. They were stolen by the Gargoyles in Ultima VI and had to be found. While re-buriable, they were essential in combination with the Vortex Cube to return the Codex of Ultimate Wisdom to the Void. After the destruction of the Sphere Generator in Ultima VII, they stopped working.

Trivia

 * Although the Moonstones first appear in Ultima V, they MUST have existed since the first appearance of blue Moongates, since they are the force behind them.
 * In Ultima Underworld I and Ultima Underworld II, spheres called Moonstones are also found. However, they are NOT the same as the eight Moonstones of the eight Moongates.