After the destruction of the second death star the rest of the Empire was in disarray. The emperor didn't have an heir to his throne because he believed that only he should be allowed to lead. In case he were to die he assigned his most trusted agents to destroy the empire. This ultimately happened at the battle of Jakku.
The battle of Jakku happened about one year after the battle of Endor. The battle lasted longer than anyone expected. The Empire had only one super star destroyer left in the galaxy. The agents of the Emperor had a plan to destroy the remaining imperial troops along with the rebellion. They knew the planet was very unstable due to ancient sith artifacts that could destroy destroy the planet along with the surrounding starships. The plan wasn't executed because the rebellion destroyed the last super star destroyer. After the battle the agents were going to travel to the uncharted territories, beyond the outer rim.
The battle of Jakku destroyed the empire but didn't destroy the rebellion. The agents of the Emperor still traveled to the uncharted territories. In the uncharted territories they found the eclipse star destroyer, the Emperor's personal star destroyer.