For I have sinned

Summary: Dean didn't understand. Penance wasn't letting go of Dean's hand and staying behind to be hunted and hurt. Penance meant letting Dean go in a world where Cas couldn't follow. SPOILERS from season 4 to 8. Oneshot.

Dean didn't understand.

It was not like Cas had tried to explain it, anyway. He left it as Dean wanted to take it; that Cas had one mother of a guilty conscience, that Cas grew a pair, that Cas was nuts. The suffering Dean felt while thinking that Cas stuck in Purgatory was his fault sufficed. He didn't need to know that in some way, he was right.

Cas tilted his head to look at the stars. Next to him, Fred Jones was quietly snoring in his wheelchair, his mind a swirl of colors and light. A small smile touched the angel's lips. That feeling of carefree contentment was very close to the happiness he had associated with the Heavenly Host for millennia.

His eyes darkened. Heaven was one of the most important reasons that drove him to stay behind and cleanse himself of the sins he had committed. He still remembered... clenching his fists as thousands of angels screamed and perished, their only guilt a fierce loyalty that, once, defined Castiel as well. Angels were built to believe and obey. Faith was crucial, faith was everything.

Castiel had lost faith.

An angel without faith... He remembered the night he snapped and beat Dean until he couldn't stand anymore. He had turned from his brothers for this mortal with sinfully, indescribably powerful eyes; green, sharp orbs that had the intensity of thousands supernovas and all disasters combined. They contained so much fire, and emotion, and hope. Something entirely human that Dean had slowly infected Cas with. So, when the hunter's eyes became empty and weary, his words ashes and mind astray, the angel realized that anger and betrayal were the easiest things to feel. My God abandoned me; I shall not allow you to do so as well.

He couldn't take out his broken faith on God, but Dean was there. Dean was all there was, because in the end, if Dean wasn't faith, he was purpose. He wouldn't have gone to that warehouse and acted as a diversion, nearly killing himself in the process, if wasn't harboring the smallest glimmer of hope.

The apologies he muttered from that hospital bed were truly heartfelt and real. Dying for Dean again at the hands of Lucifer was real. Leaving Dean with that woman and her child was torturous.

The war was getting harder and harder. He was losing, and not only fights or soldiers. Truthfully, there had been little to lose in the first place. Castiel didn't have faith in himself; so how could he lead angels in battle, angels that had faith in him the same way he did Dean?

He needed Dean's simple words, swift conclusions... Dean's presence. But he only watched from afar, because Dean was happy. Dean had a normal, healthy life, and who was he to deny him all that and drag him back into a world so devoid of his brother?

Desperation was what lead to Cas' deal with Crowley. He wanted results, he wanted to free his kind, and he wanted it to be over. When Dean came back it was too late; he'd been tainted, he had truly and despicably fallen, when the first lie passed his lips and Dean believed it. When he became a spy.

I am doing this for you. I am doing this because of you. I am doing this so Raphael cannot undo all the good things we have done. I am doing this so we don't see what we've protected so dearly blasted into oblivion.

He'd been lost; he thought he knew better, he thought he was right. Once the essence of all evil entered him, however, things stopped being so... clear.

"It sounds so simple when you say it like that. Where were you when I needed to hear it?"

"I was there. Where were you?"

Watching, needing, never touching. Suddenly, Lucifer's words rang clear in Cas' mind: I loved God too much. The Devil blamed love for his creation and the creation of evil, of all things. Cas dreaded the thought, but indeed, he resembled the fallen archangel in one aspect: he loved until it warped and twisted him to the point of near destruction.

In the aftermath, he had learned a new, vicious emotion: self-loathing. When Dean said I'd rather have you there was no other response he could have given but I'll come with you. He could try and fix everything, he had thought back then, when his mind was in pieces and he couldn't remember why it all mattered so much anymore.

When the weight of what he did crashed onto him, it was like a comet, or a meteor; sudden, explosive, growing and evolving. The first thing he had done when entering Purgatory was to leave, run, keep them away from Dean. Keep the black monstrosities with sharp teeth away. He landed somewhere near water, and the guilt wouldn't stop eating away at his being.

How? How did it become this way? How could he have known that, besides Sam's, Dean was his humanity too?

That's when he understood that it must have been God's plan; a never-ending suffering that would eventually lead to his death – punishment and penance for all the horrendous things he'd done. He remembered each of their names, the angels he'd killed, and he prayed for their forgiveness every dark, haunting night (because his head was filled with Dean's ragged prayers and he needed something to ground him). He didn't belong in Purgatory, by definition. He was a creature of light and power, a warrior of Heaven, and this was a place of abominations.

But wasn't he an abomination as well, now? In a way, he belonged here. He needed a certainty and something to believe in, other than perpetual worry over Dean's well-being.

And then, Dean found him. Crashed him to his chest with a shocking urgency, and Cas was frozen by the wave of happiness and belonging that washed over him, as if Dean's arms were the place where he was created. The smile was there, and the hope, Castiel reeled, while Dean talked about ways to get out.

He should have told him right there. Opening his mouth wasn't that hard, but he found that he couldn't, wouldn't. What did Dean say, in a time that seemed ages ago? When humans really want something, they lie.

Castiel didn't lie. Well, not outright. He lied by omission. That was a small sin compared to all the others, and he'd pay for it as well. It was Dean's fault for being so adamant about getting him out, it was Dean's fault for showing Cas he was important. It was his damn fault for spreading his arms in the air like angel wings and say I need you.

How, he had asked God then, could he have said no?

But he had let the pain and fear and anger crash into him when Dean disappeared into the blue mist, and yelling out NO to a oh-so-desperate Dean was like ripping out his Grace. But he had stayed behind, because he needed to do penance.

Penance wasn't letting go of Dean's hand and staying behind to be hunted, hurt and killed. Penance meant letting Dean go in a world where Cas couldn't follow. That was the ultimate price to pay for his mistakes. Now, there was nothing more to feed on but memories.

And then he's in Illinois, and he doesn't even have the power to stand up. His thoughts are scrambled and he's... so confused. Dean. Find Dean. He's feeling his Grace flicker and his wings barely supporting him. But his head was lucid again, and when he stared into Dean's shocked, pained eyes, he'd let his happiness seep into a small smile.

"Hello, Dean."

Yes, Dean didn't understand, and didn't want to. He was already terrified of the extent of Cas' willingness to sacrifice himself for him, and he wouldn't have understood even if it meant saving his life why one of the most powerful creatures on Earth chose to be by his side. Dying again and again, killing his own kind, sacrificing everything, staying behind... Dean didn't understand that he was worth it, all of it.

Then again, maybe even Castiel didn't. That must be the reason why he's sitting here, in silence, watching the stars his Father created next to a dreaming old man. Castiel has changed; standing next to a flame time and time again does that to you. His penance was over; now came the time to face the consequences of his actions. Now, he has to stand on his own and find himself again. Dean has forgiven him...

Now, all Castiel needs is to forgive himself.

There's so much Destiel in my head I feel like Leviathans are trying to break out – and succeeding, as you can see. I really hope you liked this little oneshot of mine. Review and tell me what you think; good, bad, as long as it's constructive, I'll gather all the reviews, sow them together and go to sleep all fluffed up in them.