Altar rooms

Seven of the major dungeons of Britannia are interconnected at their lowest levels by a series of altar rooms in Ultima IV, which are dedicated to the three principles of Truth, Love and Courage.

Description
Each altar room was linked to the four dungeons which opposed the virtues connected to the principle which its altar embodied. The Altar Room of Truth had passages leading to the dungeons Deceit (Honesty), Wrong (Justice) and Shame (Honor). The Altar Room of Love led to Despise (Compassion), Covetous (Sacrifice) and Wrong. The Altar Room of Courage led to Destard (Valor), Shame and Covetous. All altar rooms also linked to the Dungeon Hythloth which connected itself to all three Principles due to its opposition to Spirituality.

Using these altar rooms, the questing Stranger would be able to quickly traverse the dungeons of the realm, and could find their way even to dungeons whose entrances they had not yet discovered. Eventually, the hero would also use the colored Virtue Stones won through their adventures at the three altars that they might obtain the Key of Three Parts - a device necessary to the end of their quest in the Great Stygian Abyss

Trivia

 * The fastest way to access all three altar rooms is to enter the Hythloth through a secret passage in Castle Britannia, which directly leads to eighth level of the dungeon, where passages to all three altars exist.
 * Thanks to a bug in the French version of the game, the stones (like all other items in the game) can't be used to gain the key, thus making the game unwinnable.