Finally Vader broke the pace by giving several steps, chest heaving in labored breaths as he pulled back to a safer range. Luke paused momentarily, walking slowly around his father, his limp growing worse but still looking for that opportunity, some chink in his father's armor, physical or mental.
"You're tiring," Luke goaded as he circled, bringing his arm up and back, attempting to loosen that pre-injured shoulder as he swung his saber in slow arcs before him, tip to the ground.
"You're weakening," Vader ground out, aware that the boy was right.
"Not in resolve."
"You don't have to do as he commands..."
"This from the man who told me that I didn't understand--that he must obey his Master." Luke shook his head, voice rough with scorn. "Don't dare lecture me."
"You are slave to no one, Luke--neither Palpatine nor Darkness. You are beyond both. Understand that!"
"Because of you, is that what you think? Because you pushed me to this?" His son's chin came up in a challenge, words clipped by short breaths. When Vader didn't reply, realization flared in Luke's eyes. "Is this what you wanted? Is this what you wanted for me?!"
"I wanted everything for you. I would have paid any price..."
"But you didn't...I did." Luke's voice was raw with anger and accusation. "I paid the price for your ambition. Yours, not mine."
"Luke, listen to me..." Vader glanced to the doors which he knew Palpatine would soon walk through, stepping back as his son stepped forward, determined to have this opportunity, even now. To make the boy understand. "The power you hold now will gain you everything. An Empire, when you decide to take it."
"I don't want your Empire!"
"Then why were you fighting with the Rebellion? To overthrow--to take command. Everything you wanted then I have placed within your grasp. Everything."
Luke dragged broken, strapped fingers back through sweat-spiked hair, voice fraught with emotion. "You have no idea what I wanted! I was fighting for freedom, not command. From you, from him, from this--" He gestured wildly about him to the gilded opulence of the huge Palace, the grasping affluence and self-serving influence of the city-planet beyond.
It was an impassioned cry, accusation and desperation both, a momentary glimpse of the idealistic boy that Vader had faced over Bespin. Proof that he still existed in some form, no matter how tattered.
"You've made me everything that I was fighting against, and I can't step back--I can't ever go back. That person is dead! Your son died here--can't you see that!"
Vader shook his head, aware that Palpatine would be in the room in moments. "You are still my son...more powerful than ever."
Luke shook his head, manner slipping instantly from impassioned to cool, the change chillingly mercurial, that outburst of unbridled emotion completely suppressed. "That won't save you."
"I don't believe you'd kill me. I don't believe the Emperor has taken you from me so completely," Vader gambled, realizing as he finally gave all of his own tangled confusions voice, that he should have spoken out long ago. "Because everything that you are, I am. Every feeling that tears at you now, I have endured. But look at where you are...the power you hold! I did this for you--for you! The Darkness has not taken away what I feel for my son. No matter how at odds, or how powerful the Darkness, I cannot deny them. This is stronger. And everything that I feel, I know that you feel too. That is why you will not land the blow."
The boy was silent for long seconds, head low, chest heaving from exertion...
Unstable, volatile emotions flared again quicksilver-fast, Luke's reaction tearing through Vader's hope. "You of all people, you who brought me here... You have the audacity to claim affinity, any connection--a right to ambition on my behalf? You're nothing to me! Nothing!"
Luke hurled the words at his father, wild with the pain of bitter abandonment and his own shattered hope, an intensity Vader couldn't hope to counter. He charged forward, saber swinging high and back, the blow coming down with enough power to send a shock through Vader's arms and stagger him back a step as he held against it, Luke's blade still pressing home, locked onto his father's as he leaned unafraid into the wildly flaring blades, the red glare showing deep scars gouged into the pale skin of his face as ragged black lines.
Vader faltered beneath the raw emotion contained in those eyes and in that moment Luke struck out, eyes hard and cold, the Darkness answering his actions unbidden, whipping about him, power drawn to passion.
Anger, absolute outrage, gave him a speed which Vader couldn't hope to match. Every move came faster, every action leading to the next, forcing Vader into check, each attempt to free himself only taking him into another check.
Vader looked for an opening, a way to contain him so that he could bring his strength to bear, but Luke was moving too quickly, countering every parry, giving no quarter, every blow closer, reactions honed to a hair's-breadth.
Realization came in a scarlet wave of burning panic; that they were not equal...
That his son would best him.
Luke's lightsaber swung down and away as his hand rose, palm out, a whirlwind of power compressed into a single body-blow.
Realizing, Vader raised his own hand, calling the Force to counter the push, and momentarily they froze, power against power, the Force holding each of them immobile whilst pushing forward with inexorable strength, feet sliding against the smooth marble floor, unstoppable force meeting immovable object.
Raw power--Vader's bulk towered over his son's slight form at this proximity as each channeled the deluge of energy, hand out before them so close they could almost touch. Vader grunted; let out a primal sound as he brought every last trace of strength to bear.
But this was not the physical--this was a blow conceived of Darkness. His son tilted his head, narrowed his eyes...
The power--the blow which hurled against Vader in that moment--was fury unleashed, utterly unstoppable. Absolute energy directed and constrained, channeled to a single intent. It was raging emotion given physical form and even countering with the same, Vader had no chance of neutralizing or containing it.
He faltered, felt himself launched backwards as his feet left the floor, thrown against the far wall with massive force which drove the air from his lungs as his legs collapsed beneath him. He kept hold of his lightsaber as he crumpled down, vision tunneling to darkness, desperately pulling the Force about winded lungs and pounding head as Luke stalked forward, eyes burning with grim intent.
It took a second--a second, no more--to bring himself around, to force alertness and energy through failing awareness...
...The sound of a lightsaber's droning buzz overrode the hiss of his respirator.
His son stood over him breathing heavily, pale, scarred features given harsh relief in the scarlet glow, sweat spiking his hair.
His hands holding the saber shook as the bright crimson blade wavered before Vader's throat.
.
.
Palpatine stood mesmerized at the entrance to the hall, frozen in tense anticipation, waiting to see what his feral Jedi would do--whether he would walk away as ordered, or whether the desire to destroy that which Palpatine had invested so much in making him hate would drive him to openly disobey his Master and bring down his wrath yet again.