It is chaos in the throne room. The swirling darkness of the Empty rips up the marble floors, sending pillars crashing to the ground, black dust erupting all around them. The ground shakes, the walls crack—and everywhere is the suffocating darkness of the Empty, like black goo, wreaking havoc. Jack can feel it inside, the anger of the Empty, a force so strong that it's like standing too closer to a fire.
"Jack!" shouts Sam.
Jack looks up, his heart pounding wildly in his chest. Castiel is on his stomach in front of him, one hand gripping the angel blade and the other protecting the back of his neck. Sam and Dean are back to back, demon blades in hand, as the Empty closes around them. But their weapons may as well be toothpicks on a battlefield.
"You have to stop it!" shouts Castiel. "Only you can stop it!"
It's almost impossible to see what's going on, but Jack clambers to his feet and outstretches his hand. He doesn't know how he does it, but as he walks, the Empty parts and he can step through like a walkway. He meets Sam and Dean in the middle of the room. Rowena is nowhere to be found.
"Jack…" warns Dean, his voice rising with desperation.
Jack clenches his outstretched hand into a fist, his eyes glowing like suns, and the Empty ripples away from them.
"Get rid of it!" shouts Dean.
"I'm trying!" shouts Jack, scrunching his face in concentration.
There's something different about the Empty. It's more chaotic and angrier than Jack has ever known it to be. And that's when he realizes that the Empty has been restraining itself around him up until now, and what he is seeing right now down in Hell is the complete, unfiltered power of a cosmic being.
"It's…fighting me…" he gasps, throwing out his other hand.
It's like Jack is creating a force field around the Winchesters, a circle through which the Empty cannot cross. But as his strength depletes, Jack realizes with a sinking feeling that he is not powerful enough to banish it entirely from this place.
"I can't…" he gasps.
"Then get us out of here!" shouts Sam.
Careening from the high ceilings, the darkness of the Empty plunges down to where Jack stands with Sam and Dean. He raises his hands over his head and the Empty slows. Sweat drips down Jack's face and his hands start to shake. And then when another swirling mass of the Empty attempts to break through the circle, Jack finds that not only does he feel weak, but he can't even move his arm.
"Sam," he gasps.
"Get us out of here!" shouts Dean.
"I…can't…"
In horror, Jack feels his own arm moving of its own accord. His limbs are rock solid, like he is made of stone, and he can't move, can't breathe. His own shaking hand moves from defending the Winchesters to wrapping itself around his own throat.
"Jack!" shouts Sam.
Jack falls to his knees, struggling to keep the Empty away with one half of his body, while the other half rebels completely out of his control. As his own hand wraps itself around his throat, constructing his own windpipe, and Jack realizes that he has a choice—let go of his power over the Empty to save himself, or protect the Winchesters and die.
"No…" he gasps.
A slender arm of the Empty breaks through the circle and stretches its wiry black fingers towards Jack. Grunting with effort, torn between trying to regain control of his body and fending off the giant mass around them, Jack can do nothing as the arm stretches out towards him.
And then Jack feels his own arm reaching back. A yearning inside of him like he has never felt before roars to life alongside his own soul. He feels ecstatic—joyful. He wants more than anything to be with the Empty, to be with the darkness because…he is darkness.
Then the Empty touches his hand.
It's like his soul is being ripped out of his body. The force within him nearly implodes, like it has been waiting for this contact, waiting for a thousand years. His blood goes cold and his breath disappears, and all of a sudden, he's not sure who he is anymore. He can feel the Empty inside of him and he can feel her too—Amara. For a wild moment, he's not sure who Jack is anymore. For a moment, he is Amara.
And Amara is delighted.
"JACK!"
Out of nowhere, Castiel collides with him. The impact sends the both of them flying to the ground. The shock of the impact is like a jolt to the force controlling him and his hand releases his throat as they tumble across the black marble floor. Everything is undone—the Empty's hold over Jack, Amara's presence, and Jack's power holding the Empty back. And as he is sprawled on his back, seeing all of the furious mass of the Empty plunging through the air towards him, he wonders for the first time since he took Chuck's power if he's capable of dying.
But another form obscures his vision, launching itself between the Empty and Jack. The darkness of the Empty hits the body. Somebody shouts, "NO!" The darkness wraps its spindly arms around the trench coat and suspends the body in the air.
Castiel looks back, and for a sliver of a second, like time has slowed down, Jack locks eyes with the angel and sees the unspoken words in his face: let me do this.
And then the darkness envelops Castiel, folding in on itself like a black hole, until the Empty is gone completely and the throne room is flooded with silence.
Jack can hardly breathe.
"Cass!" shouts Dean, storming into the area where Castiel has just disappeared. "CASS!"
"He's gone, Dean," says Sam.
A string of flowery curses erupts from a figure climbing out of the rubble—Rowena, dust in her hair, and tears in her dress.
"Are you alright?" asks Sam to Rowena. "Are you hurt?"
"Oh, I'm seething," she hisses. She pushes a curl of hair roughly behind her ear. "You break into Hell, you step on my property. The Empty wants war with me—the Queen of Hell. This is personal now!"
Dean isn't listening to the conversation. He bounds over to Jack, still prostrate on the broken floor, and grabs his collar, lifting him partially off the ground.
"Dean!" shouts Sam.
"You bring him back," growls Dean, his face inches from Jacks. "You bring him back right now."
"Dean, that's enough!" says Sam. "Let him go!"
Jack opens his mouth to respond, but a swell of sickness rises in him and he pitches sideways and retches. Dean lets go of him as Jack struggles to right himself. He is shaking and cold, like his veins are filled with ice, and his skin is sticky with cold sweat.
Sam crouches down by him and puts a hand behind him, helping him sit up. "Jack, what's happening?"
Jack swallows down the rising bile in his throat and takes a few deep breaths. He feels a panic rising in his chest, panic because Castiel was taken in front of his very eyes, and because he knows that something is different than before.
"Castiel," he whispers.
But he knows that it won't work because he can't see the Empty in his mind like he had been able to do before. He can't sense Castiel's spirit anywhere. It's like a wall is up.
"He's gone," he breathes.
"But…you can bring him back," says Sam. "You've done it twice now."
"I can't," he says, shaking his head which has begun to pound painfully. "Something's wrong. It's like I'm blind—I can't feel him anywhere."
"So what, he's just gone now?" shouts Dean. The desperation is clear on his face.
"No," whispers Jack. "He's in the Empty. He made a deal with it to protect you, Dean, and now the Empty has taken him back. He's not gone. He's a hostage."
"What are you saying?" says Sam.
"I'm saying the Empty is trying to make a deal with us," says Jack. "A trade."
"A trade?" says Dean.
"Amara for Castiel," says Sam in understanding.
"The Empty knows it can't force me to release Amara," says Jack quietly. "And now that it's this angry, it isn't letting me take Castiel out like I have before. It's obvious what I have to do."
"No," says Sam immediately.
"I'm going," says Jack. "It's the only way."
"You're going to the Empty?" says Dean.
"I have to."
"It's a trap," says Sam emphatically. "You can't do this!"
"Do you want Cass back or not?" snaps Jack.
To this they have no reply.
Jack clambers to his feet unsteadily. He still feels sick. He hates that Amara is fighting him, that she would be so convinced by the Empty and its calling to her.
"You can't go like this," says Sam desperately. "Amara still has some control over you. You're not at full power." Then he adds as a last plea, "Let us come with you."
"No," says Jack firmly.
"Jack…" says Dean warningly.
Jack looks to Rowena apologetically. He snaps his fingers and the destruction of the throne room is immediately restored to its old state.
"I'm sorry for bringing this here," he says, and raises his hand again.
"Don't do this," begs Sam.
"You'll be back in Heaven," whispers Jack. "Where you belong. You could have all died here. And I can't let that happen again."
"Jack!"
SNAP!
The throne room disappears, as do Sam, Dean, and Rowena. Everything is gone, and around him, there is nothing but Empty.
Hope you are enjoying where this is going!