Key of Three Parts

The Key of Three Parts – sometimes known as the Tripartite Key or Key of Infinity – is an artifact fashioned from three components – the Key of Truth, the Key of Love and the Key of Courage. Once fully assembled, it unlocks the chamber of the Codex within the Great Stygian Abyss. It appears in and  Ultima Underworld.

Description
The three pieces of the tripartite key were initially housed in the altar rooms which lay beneath Britannia's great dungeons. Each of the altars within these chambers represented one of the Three Principles, and was fitted with four depressions which were designed to house several of the Stones of Virtue. The Stranger, on the quest toward Avatarhood, would need to collect these stones and install them in the altars to which they corresponded, as doing so would allow access to the three parts of the key. Eventually, after passing through the numerous trials of the Abyss, this device was used to procure the Codex of Ultimate Wisdom and attain the mantle of the Avatar.

Years later, during the Avatar's imprisonment within the Abyss by Baron Almric, the hero would once more have need of the Key of Three Parts, so as to reenter the dungeon's innermost chamber and thereby prevent the release of the  daemon known as the Slasher of Veils. However, the key had again been split into three pieces and scattered throughout the Abyss. The Key of Courage lay within a chamber fraught with terrible beasts. The Key of Truth had been bound to the shrines of the dungeon, such that it could only be retrieved through use of a specific mantra. The Key of Love, for reasons unknown, would only appear when the tears of a bereft lover mixed with the magma of the volcanic dungeon.

Eventually, the Avatar retrieved the three parts of the key and reassembled it once more, and was thereby able to again enter the Chamber of the Codex, wherein they used the eight Abyssal talismans to banish the Slasher of Veils back to the plane from which it had come.