Supposedly the greatest achievement of Jerni technology, the Eternity Crystal was rumored to possess the ability to reverse time following a catastrophic occurrence, and to steer the current timeline towards a more favorable outcome.
Rumor had it that the crystal was concealed within the Jerni ruins located close to Adony Station; however, it was ultimately revealed to be an elaborate deception orchestrated by Darth Vader in an effort to eliminate Luke Skywalker and Leia Organa.