Great Stygian Abyss

The Great Stygian Abyss, situated on the south part of the Isle of the Abyss, is the darkest and most evil place in Britannia. The Abyss is the antithesis of all good things, opposing all of the virtues at the same time. Dark creatures of unbelievable evil, balron lords, aggressive dragons and numerous other monsters inhabit this hole of evil. This makes the Abyss a place to be avoided at all costs, for only the most virtuous person won't forfeit their life as soon as they enter.

Regardless how many times the whole Abyss is destroyed, evil always resurrects itself in an even worse form than before. A possible reason for this may be the fact that the walls between dimensions are thinner in Abyss than anywhere else in Britannia.

For a solution of the hardest puzzle in the Abyss, see Abyss Room Puzzle.

History
In Ultima IV, the Stranger, trying to complete the Quest of the Avatar, had to descend through the Abyss to find the Codex of Ultimate Wisdom, since the Abyss was connected to the Shrine of Singularity which housed the Codex. In this time, a strong pirate fleet resided in the west bay of the Isle of the Abyss, the only possible access to the entrance of the Abyss. The Wheel of the HMS Cape could be very useful here as it would make a ship strong enough to fight past the pirates; it was also possible, but very difficult, to achieve this without the Wheel.

The dungeon was situated in the middle of a huge volcano, and could only be opened using the Book of Truth, the Candle of Love and the Bell of Courage. The Skull of Mondain could supposedly be destroyed by being cast into the Abyss, and according to Erethian, the Stranger did throw it in. However, a skull claiming to be this same one appeared later in Britain's Royal Museum.

Only magical weapons would work inside the Abyss. In order to get from one level down to the next one, one had to use the correct Virtue Stone on the altar found inside each level. It was clear that the dungeon was not a natural formation but artificially built.

After the Codex was pulled up to Britannia, and the lava had cooled down, the Shrine of the Codex was built to seal the entrance to the Abyss. In Ultima Underworld I, Sir Cabirus had erected a colony in the Abyss, using another entrance. But the colony degraded into a prison, with several scattered settlements inside. After the Avatar travelled there and stopped the evil wizard Tyball, everything sank into boiling lava.

The Abyss is the last dungeon visited in Ultima IX. The Avatar has to use Pyros to enter it and travels through four elemental areas before going down into the Abyss itself to find Lord British and Lord Blackthorn in a duel.

Trivia

 * Although unvisited in Ultima III the Abyss is mentioned in the introduction of The Book of Amber Runes:


 * The need for a "Bell, Book and Candle" in order to open the Abyss is a reference to the bell, book and candle method of excommunication of the Catholic Church. Other videogames, such as Zork and NetHack also make use of these three items in order to access evil or hell-related places.
 * In early drafts of Ultima IX, the Abyss was accessed deep beneath the ocean near the Isle of the Avatar, via a diving bell. Teeming with daemons and riddled with lava lakes, boiling mud, and ancient ruins, the vast complex of hellish caverns housed an iron keep as well as one of the Guardian's columns.
 * In Runes of Virtue, the hero must descend into the Great Stygian Abyss to recover the Rune of Humility. The Great Stygian Abyss is also where the Black Knight hid the Mystic Armour, which he had obtained through nefarious means, and the hero could recover this fabled armour.