A/N: Thank you to Olivia, Fated, Deanna, and Grace for looking this over for me.
It takes three days for Castiel to kill Dean Winchester the first time.
He knows Naomi is watching, waiting, though he's not quite sure why she isn't interfering.
Three days of Dean's voice pleading, begging. Three days of those wide green eyes staring at Castiel with hurt and fear. Three days of Castiel running away every time it gets to be too much. Except that he can't really run away. Every time he tries he ends up right back where he started, some trick Naomi's playing, and Dean's wide and panicked face is always right there.
In the end it only lasts three days because Castiel manages to tell himself it's not really Dean. That if he just gets this over with Naomi will let it be. And even so, even with those reassurances, Castiel still clutches to the fake Dean's body and weeps. And just when he starts to calm down, another Dean walks into the room.
The second time is over almost as soon as it begins. The emotion Castiel is caught up in helps fuel the attack. The third and fourth ones arrive so quickly the same thing happens. Castiel watches the life leave each fake through a filter of tears.
The fifth one is different.
Confused, grieving, hurt and not just a little angry, Castiel sees the fifth Dean and immediately collapses. His angel blade slips from his fingers, falling to the floor with a clatter, and he drops to his knees, burying his face in his hands.
"I can't," he breathes through the heaving sobs. "I won't."
The fifth one doesn't die by Castiel's hand. It dies by Naomi's. She appears suddenly and stabs Dean in the heart without hesitation. Castiel is sure he can feel her blade slicing through his own chest as he watches.
As he gasps and whimpers, Naomi turns to Castiel in disgust. She picks up his blade and holds it out for him, expression stern.
"You can. And you will."
The sixth Dean... Well, it's impossible to compare in terms of which time is worse. But the sixth time is particularly bad.
The sixth Dean enters as Castiel still stares at the proffered blade. His eyes flit to Dean in panic. Naomi thrusts the blade closer to his face.
"Take it, Castiel. Kill him. Now."
She must see something in Castiel, something that tells her he simply refuses to comply. Because instead of continuing to push the issue, she jams his blade back into his unwilling grasp and, keeping her hand wrapped tightly around his, yanks Castiel to his feet and physically forces him to kill Dean.
Castiel can feel the blade rip through Dean's flesh. He can feel the resistance of cloth, skin, muscle, and bone give way under his hand, forced along by Naomi's push.
He's sure that if he were human he would puke.
The seventh time proceeds in much the same way.
As does the eighth.
And the ninth.
And the tenth.
After that Castiel loses count.
At one point Castiel decides to fight Naomi. Not so much in the attacking manner-he can't allow himself to be the cause of more angel blood shed, no matter what she may be doing to him-but he wrenches himself out of her grip. The new fake Dean is just entering the room as this happens and seems utterly confused, like he hadn't been programmed for this situation. Castiel looks to Naomi, expecting her to take care of the Dean, but she ignores him, her eyes fixed instead on Castiel.
Castiel remembers the weight of the blade in his hand quite suddenly. He glances down at it and an idea forms.
He can get out of this.
All he has to do... is drive his blade through himself. Let it tear through his grace.
It's fine. It's good, even. It'll end. Everything. There's no after for an angel. It'll just end. And that's fine. That's good. Castiel sort of looks forward to it.
His grip on the blade tightens, and he starts to raise it, ready to make the final blow-
When he's suddenly back in the chair. Naomi's chair, the chair in her office, and her blade is there, just above him, and she's drilling, and Castiel screams.
He doesn't have suicidal impulses again. Naomi manages to erase that. Or at least bury it deep enough. Underneath everything else she dredges up. Castiel barely has a moment to regain his breath before she throws him back in that room where the dead bodies litter the floor, and another Dean walks in.
There are still Deans that Naomi has to force Castiel to kill. Castiel still throws her off after one too many. He still breaks down. But there are the select few Deans that are a success. Castiel can kill them. In a fit of rage at his situation or after a few moments of hesitation and talking himself through it, Castiel can kill a few Deans here and there. Naomi seems pleased.
Steadily it grows easier and easier. Castiel tries to get himself to stop thinking about it. He's a warrior. A soldier in the army of God. A simple kill is nothing to him. It is instinct.
Dean becomes more of a challenge. Sometimes he fights back, strong and a warrior.
Castiel learns to disable him before he can fight.
Sometimes Dean pleads with Castiel, broken and a child.
Castiel learns to ignore it. A few times he even manages to finish the kill before the pleading can start.
Bodies continue to pile up.
Castiel grows numb.