In Palpatine, a mind trained by the Sith arts and years of political experience, he searched for another way out. Deciding that he might be able to convert the son by taking the place of the father, he launched a new attack, this time at Vader.
The jagged blue bolts danced from his fingers, and lanced toward his former pupil. Vader knew that the emperor would see him dead rather than converted, and was prepared for the attack. When it finally came, the defense that he had prepared crumbled. In its place was a torrent of frustration, and rage born of decades of his own plans and aspirations being thwarted. The feeling of losing himself in the will of this monster for years came to him, unleashing energies he didn't imagine he could touch, much less control.
The deadly force lightning seemed to fizzle as it arced toward him. The strength of the force flowing through him did not need a gesture or a plan, his will was enough to guide it. The attack was blunted with an ease Vader could not have imagined moments before.
Palpatine took another step back at this display of unity with the living force. Vader pressed in for the kill.
"Your time is at an END!" Vader screamed the last as the emotions flowed through him, taking the form of blue lightning at the tips of his fingers, and leaping toward the emperor.
Palpatine screamed as the power contained in the bolts drove home in his weary frame. He tried to fight the desire to lose consciousness as the pain enveloped him. He struggled to find the dark heart of his magic, born from years of striving to control those around him. The confusion and pain enveloped him, drawing him away from the force, back into his body, which was being mercilessly electrocuted by Vader.
Luke watched passively as the emperor writhed on the floor. Part of him wanted to join his father in ending the foul life that had destroyed both their lives, and part of him wanted to leave and let the hatred consume them both.
Vader approached the downed emperor and lifted him easily by the robes. Drawing on an anger that had been stifled and redirected for 3 decades he freed one hand from the robes of the man before him , and grasped his throat.
"This has been waiting for many years", and releasing his touch on the force to everything except suppressing Palpatine's power, he used all the physical strength in his remaining human arm to slowly crush the windpipe of the emperor.
As he felt Palpatine's throat start to collapse, Vader channeled all the rage and hate and frustration of decades of forced servitude back into the cause of that suffering.
Palpatine eyes widened as the raw emotion of his former pupil bored through his mental shielding like a knife though butter. The power of the emotions driving at him though the force began to overload his brain and his spirit. In the final instant before life left him, he saw the true nature of what he had done reflected in the blank face of the force and his attacker, but there was no one to tell, as his lifeless form was hurled over the railing into the reactor core.
"Father..." Luke began.
Vader turned.
"We must leave, this place is doomed."
The hanger bay was in chaos as Luke and Vader made their way through it. The Alliance was clearly making headway in their attack on the Death Star.
Luke was helping Vader across the shuttle bay to his personal Lambda class shuttle. It sat alone in a reserved part of the hanger. The techs rushing to and fro cared little for them or their mission, if it wasn't a combat ship dedicated to the defense of the station it wasn't worth notice.
"Is the shuttle fueled, father?" Luke gasped under the additional weight of the armored figure.
"Yes, it is maintained as soon as it touches down" Vader rumbled back.
"Where are we going to go? The Alliance will hold you as a war criminal, and the imperials will shoot us on sight once they know what has happened"
"I have a plan, get us to the Executor" Vader replied.
The control room completely ignored the shuttle as it lifted from the deck and made its way toward the mag lock. The comm techs manning the boards were at that time more concerned with the news coming over the boards that an Alliance strike group had made its way into the internal structure of the station, and had evaded the pursuing TIEs.
Vader lay slumped in the co-pilots seat, breathing heavily through the respirator. He reached out to Luke.
"Tune to frequency 3274.6, and transmit this code..."
"Sir, an emergency message coming in from Executor-One on the grey channel" a crewman in the pit called to Captain Piett..
"I'll take it at my comm." He replied with an edge in his voice.
As the Captain settled into his comm chair and opened the displayed frequency, he was startled to see Lord Vader sprawled into a flight chair on the shuttle.
"Captain" Vader began. "We are in a desperate situation, and require that you tractor us aboard immediately. After which, you will jump for the coordinates that I am sending .now. Know this. The Emperor is no more, I am the highest ranking authority in the Empire. Do not fail me Captain". The transmission blacked out.
"Defense and Capture officers, I want that shuttle brought aboard safely, NOW" Piett barked. The commands for those stations sprang into action.
The turbo laser and fighter screens shifted positions, covering the exposed shuttle until it reached the massive SSDs shielding, and broke off to rejoin the battle as quickly as possible. Once in the protective shadow of the SSD the shuttle was grabbed by the invisible hand of the tractor beam.
Once the shuttle was inside the massive hanger bay, the SSD seemed to pivot and flicker as it jumped into hyperspace, leaving its unlucky TIE crewmen to their fates with the battle unfolding around them.