Exodus

Exodus is a malevolent entity created by the magician Mondain and his lover Minax. Frequently considered the "child" of their union, Exodus' exact nature has long remained an enigma, as it is a construct clearly comprised of both organic and synthetic parts. In later years, it was revealed that the creature's two primary components were the "Psyche," which contained Exodus' consciousness and desires, and the "Dark Core" which contained the sum of the hellspawn's accumulated knowledge. The exact interface which allowed these two parts to interact and to co-exist as a sapient individual, however, has never fully been explained, having been destroyed in the course of the Stranger's questings during Ultima III.

Biography
It is unclear as to exactly when the being which would become known as Exodus was first formed, as scant record exists of the hellspawn's creation, which was chronicled only in fragmentary writings found in the ruins of Shadowguard. Whatever its origins, the nascent entity appears to have found itself orphaned soon after its "birth," as both its makers were slain by the Stranger. Determined to avenge the memory of those who had forged it, the daemon-machine waited patiently as it accumulated information - slowing learning about everything in the world around it, from the color of the sky on a cloudy day to the secrets of manipulating the fabric of Sosaria, itself.

When it was ready, Exodus began its campaign of revenge, raising for itself a dark citadel as it birthed the Isle of Fire from deep under the oceans. Powerful enough to snatch the Great Earth Serpent, itself, from the Void to serve as his protector, the evil being turned the creatures of the land to violence, summoning hordes of monsters to plague the land which had once seen its "parents" fall. In this third Age of Darkness, Sosaria saw the destruction of the mercantile fleets by pirates, the regrouping of  orcish raiders against humanity, and ill omens in both the skies and seas.

Eventually, Lord British sent his trusted friend Shamino on an errand of discovery to Exodus' newly arisen island, hoping to glean the meaning of all of this auspices - however, while the ranger eventually returned from his mission, the contact he had endured with the hellspawn rendered him temporarily insane, unable to fully communicate the horrors he had seen. In the days before the Stranger's eventual appearance, a derelict ship was towed into port, bearing no evidence of its crew save for the letters of Exodus' name written in human blood. In desperation, the young monarch of the realm invoked the powers of his amulet, summoning once more the champion who had laid low the evils of Mondain and Minax.

The Stranger, once more tasked with Sosaria's salvation, undertook the quest of Exodus' undoing with three unknown companions. This company, with the aid of the Time Lord, eventually was able to penetrate the daemon-machine's stronghold that they might destroy the interface connecting its component parts - tricking it into enacting its own destruction with Four Cards representing the concepts of Sol, Moons, Love and Death. Once thus confounded, Exodus' psyche broke from its core, unable to sustain the link between them. The Stranger and their company never spoke again of what they had witnessed.

Existence After Death
After this separation, the Gargish race managed to remove Exodus's psyche from its place in the Void, and placed its consciousness it into their Shrine of Diligence, convinced that its existence of ongoing exploration and striving made it a fitting representation of the Principle. It was here, upon the gargoyle homelands that the Avatar found it in Ultima VI. In this meeting, it explained to the hero that it now regretted her actions, having had time to comprehend their full weight. It explained that while operational, its diligence in enacting its revenge had eventually become a more pressing part of its being that the goal of vengeance itself - leaving it purposeless and adrift. It cautioned its former adversary to always keep sight of their actions' ends, so as to not lose themselves in diligence without focus.

After this encounter, the gargoyle's lands were eventually destroyed, leaving Exodus' psyche to wander the Void again. Eventually, through the intervention of the mage Erethian, the Isle of Fire rearose from the sea into which it had long ago sunk, bringing Exodus' Dark Core once more to the world's above. This dangerous chain of events gave rise to the possibility that the psyche might reunite with its mechanical core, allowing the daemonic construct to recreate itself. The Avatar, eager to guard against such a cataclysmic possibility, eventually contrived to banish the core into the Void using the Talisman of Infinity such as that the two halves of the creature could not reunite on the material plane.

Trivia

 * In the manga written by Seiji Tanaka while embellishes the narrative of Ultima III, Exodus' origins are different, with the character being an archaic god of destruction which was sealed away by the other deities native to Sosaria. Tanaka's artistic rendering of Exodus have a decidedly Lovecraftian slant, showing the daemonic entity as a mass of teeth and eyes.
 * In the plot of Ultima Online 2, Exodus is a remnant of an Overlord technology from the future of Britannia which had been sent back in time following the magical cataclysm that create New Britannia.