Shrine of the Codex

Description
Located on the south of the Isle of the Avatar, surrounded by high mountains, the Shrine of the Codex is built over then entrance of the Abyss, which is no longer active. Two magical guardians guard the only entrance to the valley with the shrine, allowing only someone on a sacred quest to enter. Inside the Shrine, the Codex of Ultimate Wisdom waits to relay its knowledge.

After the Codex was sent back to the Void, the only way to view the Codex is, to use the Lenses, in conjunction with the Fames of Infinity and Singularity, to see the Codex in the Void.

History
The Codex was drawn to the surface by the High Council after Ultima IV. This also caused the Abyss to cease activity. Over the Abyss, the Shrine of the Codex was built.

In Ultima V, the Codex was found there, and only was a sacred quest, it was allowed to enter. In the end, the Codex gave an important clue to finding Lord British. The Codex was still there in Ultima VI, but in the end, had to be sent back to the Void to bring peace to the land, after gaining a sacred quest to pass through the stone guardians.

It is unclear what exactly happened in Ultima Underworld I with the shrine, where it was totally ignored in intro and extro, but it was still there in Ultima VII, but the stone guardians had ceased to function, allowing every to leave and enter as they pleased.