Mystic Weapons

The Mystic Weapons are the only weapons that work in The Abyss and in dungeon Doom. They appear in Ultima IV and Ultima V', as well as in the Nintendo port of Ultima III.

Description
The greatest works of Zircon of Minoc, the Mystic Weapons were first found by the Stranger and Companions, after all eight Shrines gave the Stranger partial Avatarhood. Following several clues, they were able to eventually learn their location from Lady Tessa. These special swords were found in Serpent's Hold, in a secret place under the training hall. With the help of these weapons, they managed to finish off the foes that blocked their way in the Abyss.

Thought lost after this, the Avatar found them again in the Underworld in a lava pool under the Abyss, near the dungeon Hythloth. These weapons again proved their worth, taking down the foes in dungeon Doom.

It is unknown what happened to them after this.

The Ultima 6 Project
In the The Ultima 6 Project, the Mystic Weapons could again be found in the basement of the Lycaeum. However, this time it was only one of them.

Trivia

 * In Ultima IV, retrieving the Mystic Weapons grants (only) the player's character 400 XP.