Age of Darkness
Exodus diligently spent upwards of twenty years exploring and examining the world surrounding it, that it might enact vengeance for the deaths of its progenitors. Each piece of data it collected was stored in a component known as the Dark Core, which served as the daemon-machine's memory. Unfeeling and without motivation, this inert relic nevertheless housed a massive array of facts, from complex inner workings of the Britannian planet system to the color of the sky on a particular day. It's counterpart, the Psyche, held Exodus' emotions and personality, and it was the combination of the two components that made up the sum of the hellspawn's mind. In Ultima III, the Stranger managed to sever the connection between the Psyche and the Core by tricking Exodus into its own destruction using the Four Cards.
Age of Enlightenment
Shortly afterward, the Psyche was snatched from the Void by mystics of the Gargish race and installed within a Shrine in their homeland, where it served as an embodiment of the Principle of Diligence. Decades later, however, the collapse of the Britannian Underworld in the years after Ultima VI freed the Psyche to roam the Ethereal Void. From here, the Psyche slowly attempted to reunite itself with its Core, and during these years, a knowledge hungry mage known as Erethian made his way to the underwater Castle of Fire that housed the Core, making it the obsessive object of his study. 
Age of ArmageddonIsle of Fire from the sea, the magician bided his time, carefully observing and waiting. The Avatar, however, eventually investigated the newly resurfaced island and began to meddle in such affairs, eventually finding a means to banish the Core into the Ethereal Void using the Talisman of Infinity. Erethian, enraged by such actions, desperately attempted to counteract this with a spell, but succeeded only in blasting himself into naught but charred bones when his incantation backfired. Once in the Void, the Core could never again conjoin with the Psyche on the material plane.
- The Dark Core serves as the inspiration for A New Breed of Dragon's interactive fiction, Ultima: The Dark Core.
- Erethian. Underworld Dragon's Ultima VII Transcript. Ultima VII. "Exodus, interface, Dark Core, Psyche".
- Demarest, Ken et al. A Guide to the Isle of Fire (Forge of Virtue). Origin Systems, Inc.: 1992.
- Erethian. The Dark Core of Exodus (Ultima VII - in-game).
- Erethian. Underworld Dragon's Ultima VII Transcript. Ultima VII. "the Psyche returns".
- Erethian. Underworld Dragon's Ultima VII Transcript. Ultima VII. "Talisman of Infinity".