Set in 5.10
I do not know where this came from.
Even with his grace twisted and stained, the Morningstar is still the most beautiful thing that Castiel has ever seen.
There's a feeling in the pit of his stomach Castiel knows is called lust. The fact that he can feel it is a result of his fading grace. It's the same reason he can feel the heat of the ring of holy fire against his skin in a way he wouldn't have been able to a few months ago.
Lust is a sin.
"Lucifer," he replies to the Morningstar's bland greeting. His voice is deeper and rougher than usual and Castiel can feel the weight and texture of it in his throat.
He's vaguely proud of himself for being capable of speech.
Pride is also a sin; he's falling faster every day.
His knees almost give out when Lucifer says his name. Beyond the vessel's mild tone Castiel can hear an echo of Lucifer's true voice. There are not words in any of the languages Castiel knows to describe it.
He wants to shut his eyes and wrap himself in it. He wants to taste the skin of Lucifer's vessel's neck and feel the stubble beneath this tongue. He wants to press himself against Lucifer's wings and bury his face and fingers in the feathers.
He can see them, the wings. Lucifer's wings are in this plane of existence no more than his own, but he can see them out of the corners of his eyes. Faint movements in the shadows revealed in fragments by the flickering fire lapping heat onto his face and hands and thighs.
Castiel wants.
Briefly he wonders if Lucifer is trying to seduce him. Then he remembers that if he were still a proper angel he wouldn't be feeling this heat in the pit of his stomach or the dryness in his throat. He resists the need to lick his lips.
He's achingly aware of the vessel's eyes on his. He can sense the true gaze behind Nick's the same way he can hear the voice and see the grace.
He wants that gaze all over him while he's spread out, naked and shivering. He wants desperately to be invisible and somewhere else, somewhere he can't feel the electricity along his spine every time the Morningstar moves.
For his part, Lucifer seems unaware of Castiel's thoughts. He just keeps up his slow walk with legs and hips that Castiel wants in his hands and speaking with that voice that drips heat under the collar of Castiel's shirt and spreads it across his back and beyond until every square inch of his skin is hypersensitive and burning.
Castiel's acutely aware of every breath he takes and the fact that the only thing touching his skin is the cheap fabric of Jimmy's suit where he longs for hands and teeth and sweat-slick skin.
He wants.
But he won't do anything about it. He knows that even as he fantasizes about being on his knees before this being, fingers tangled in his hair, twisting and tugging. Because he fell for something more than this.
He did not start his descent into humanity for lust or temptation or his own interests. He's falling because he believes in something better. He's falling because he believes in Dean Winchester and all his flaws and sins and perfection. So he will not give into this.
But he knows the next time Dean Winchester takes him to a brothel he won't try to ease suffering; he'll lose himself in the offered sin. He'll shut his eyes and remember fire, the shadow of wings, and a voice that could break hearts.