Cube Generator

The Cube Generator is one of the three colossal blackrock structures utilized by the Guardian to prepare Britannia for his coming in Ultima VII.

Description
Appearing sometime after the founding of the Fellowship approximately twenty years prior to the Astronomical Alignment, the Cube Generator functioned to broadcast the voice of the Guardian to the people of Britannia, allowing the Destructor of Worlds to manipulate those he had earmarked for his service. The seemingly internal monologue of the Guardian's voice within people's consciousnesses eventually wormed its way into Fellowship ideology, with officials claiming that this "inner voice" helped adherents gain their full potential.

Located deep within the caverns of the island containing the Meditation Retreat, this generator was protected by a piercing wall of sound, which rendered injury and death to those approaching it without adequate equipment to shield themselves. After being informed of this device by the Time Lord, the Avatar worked to construct helmets of the rare mineral, Caddellite, that this outer defense might be penetrated. The hero was eventually able to enter the Cube to find a strange labyrinth of bridges and magical traps, and became subject to the Guardian's constant taunts while working toward the construct's center to dismantle it. Eventually emerging victorious, the generator was shattered and the small cube-shaped prism retrieved from within it.

Armed with this miniature cube, the Avatar was able to coerce the Guardian's disciples into speaking the unvarnished truth, and was thereafter able to extract information as to the location of the elusive Hook.

Trivia

 * According to the Time Lord, the three blackrock generators were sent to Britannia from the Guardian's home-world; indeed, while developing, Richard Garriott envisaged Britannia's would-be conqueror to have originated from a race of omniscient, godlike entities who might themselves eventually become antagonists in the series. This, however, would later be superseded by Ultima IX: Ascension, in which it is stated the Guardian coalesced out of darkness purged from the Avatar in the final moments of Ultima IV: Quest of the Avatar.
 * The shapes of the three generators (a cube, sphere, and tetrahedron) form the logo used by Electronic Arts from 1982 to 1999. Richard Garriott has since given conflicting statements, both denial and confirmation, as to whether this was conceived as intentional symbolism.
 * The Cube can technically be accessed without Caddellite helmets after completing the Forge of Virtue add-on. The generator's defense inflicts 31 points of damage, normally sure to exceed the standard hit point limit of 30 for any party member and cause death; however, the Avatar's maximum can be raised to 60 by Lord British upon the expansion's conclusion, sufficient to withstand the deadly sound unprotected.
 * In the SNES port of Ultima VII, the Cube Generator is located in the dungeon Undertaker. It has no defenses aside from the barrier of sound, and may be dismantled by removing the cube prism from its nearby pedestal. The generator is also much smaller and not even black.