Lenses

These two, special lenses are the only way to read the Codex of Ultimate Wisdom, which resides in the Etheral Void after Ultima VI. The blue lens is for the humans of Britannia, the purple for the Gargoyles.

The convex Gargoyle lens is old. Naxalitor originally used it to draw the Codex from the Void. At the time of the False Prophet, it was broken and resided in the museum. The Avatar let the Gargoyle lensmaker repair it so that it was useable for his quest.

The concave human lens is not as old. The Avatar ordered a lensmaker in Moonglow to make it from a Glass Sword.

Both lenses were used together with the Vortex Cube, the eight Moonstones and the Eternal Flames of Infinity and Singularity to return the Codex to the Void. Human or Gargoyle can still read the Codex at the shrine with the fitting lens. By the time of Ultima VII however, they were moved to the museum. In Forge of Virtue, it was revealed, that the lenses can draw forth and send back objects to and from the Void, such as done with the Talisman of Infinity and the Dark Core.

The concept of the lenses was screwed up in Ultima IX, the lenses had now a different function, were not round anymore and far too small.

Trivia
In Ultima VI the Avatar is instructed to place the Concave and Convex Lenses midway between the Codex and the two Eternal Flames. This was meant to focus the light of the flames upon the Codex. With real world physics, however, placing the two different lenses halfway between the lightsource and the object would not have worked as the game intended.