Time Machine

The Time Machine is a mysterious device of unknown origin, capable of bending time and space to send its user back to the past or into the future.

Description
During the events of Ultima I, Mondain's power had already come to its end some time near to a thousand years within the distant past, at the hands of a time traveler. In order that this epic outcome might happen, the time machine had to be utilized in the future, as it was capable of transposing one person back to the moment at which Mondain's Gem of Immortality was still incomplete, and fulfill the demise of the wizard. The hero shattered it before the mage could fully partake of its power. The hero struck Mondain down shortly afterward, and time marched forward through the centuries as the time traveler was overtaken to a strange sleep.

One thousand year later, Lord British summoned a champion from another world, identical to the sleeping time traveler. The Stranger, endeavoring to vanquish Mondain, uncovered the knowledge of the machine's hidden location from one of the eight princesses imprisoned by the feuding lords of Sosaria, all who for reasons unclear had knowledge of the device (it is possible that they were the original owners of the time machine). These women only gifted the hero with this knowledge after the Stranger had attained the rank of "Space Ace", having slain twenty of the star-walking horrors which Mondain had conspired with beyond the heavens.

Four different gems of varying hues were further needed to power the craft, and these were found in the possession of the rulers that held the princesses in captivity. The ruler of the Castle of the Lost King, the lord of Castle Rondorin, the King of the Black Dragon and Shamino Salle' Dacil each had one of these strange gems, but only would bestow them upon the wandering hero in exchange for tributes of service, demanding that a number of foul creatures be slain before they gave up their treasures to the Stranger.

Eventually, the Stranger managed to activate the machine, hurtling back to the crucial moment in Mondain's Fortress when the gem was completed. The machine was never seen again, vanishing into the ages past, nor the eight princesses were seen anymore. Shortly after, the time traveler awakened after a thousand years sleep, to the congratulations of Lord British.

Trivia

 * One actually can get multiple time machines by rescuing multiple princesses after knowing what do and becoming a space ace.