Originally posted by SunRazer
He came back afterwards and regained his physical form by TCoPL, lol. It could've been anything from between RotJ and TCoPL, and Sidious still had some loyalists. Wasn't the blockade of Dathomir a secret operation?
Not really, Sidious sensed her powers before Rotj.
But the Emperor, who sensed Gethzerion's power through the Force, realized that once Gethzerion mastered the controls of a shuttle, she could reach the orbiting docking facility, and from there spread her influence to the rest of the galaxy, one day perhaps even challenging him.
The Emperor ordered the orbital docks destroyed, abandoning the lmperial forces of the penal colony to Gethzerion and the Nightsisters. Ships were assigned to periodically the planet and make orbital scans to ensure that the Nightsisters were still confined to Dathomir, but we given strict orders never to land. This state of affairs continued for many years, until the death of the Emperor. Imperial Commander Zsinj, now a power-hungry warlord, returned to Dathomir pursuing the smuggler turned war hero Han Solo, who had kidnapped Leia Organa to prevent her from marrying the Hapan ambassador Prince Isolder.
Taken from The Dark Side Sourcebook
And unless you want to argue this is referring to Palpatine's DE death, he trapped Gethzerion years before Rotj, which should also be obvious from the fact that the quote mentions a commander who returned to Dathomir in COPL. Palpatine's death however is mentioned before that event.
Which means pre prime Vader is above Gethzerion as well. 👆