Utilising an elaborate plan called Operation: Cinder, Palpatine attempted to kill off the galaxy once again with his powerful weapons.
This plan was, of course, brought to an end by Skywalker once again, prompting a new mission for Luke to track down and kill the rejuvenated Palpatine.
The brand new book from Disney titled Shadow Fall details an as-of-yet unheard of consequence of Skywalker’s victory against Operation: Cinder.
The novel goes on to explain that the Empire had mapped out the Unknown Regions, and destroying their supporters meant he had inadvertently lost all track of Palpatine and his whereabouts.
source: express.co.uk