AN: Spolier for 5x13!!
In the background he could hear cars braking, tires squeaking, horns. Somebody was taking. But the noises were muffled, suppressed by the other sensations Castiel was feeling. He had been hurt in battles before, injured, nearly ripped apart. But this time it was different. His connection to the vessel was so strong, he had become that physical – like a human. Like them he felt the pain of his injuries. Fresh, throbbing, spikes of sharp agony whenever he took a breath mixed with a dull sensation of pressure inside his chest, his stomach. The Angel tried to breath through it like he had seen so many other humans doing before. His head rested against something cool behind him, the same thing he was propped up against. He did not notice how his gaze was cast up onto heaven as he tried to calm his breath, tried to stop the panting. It did not work. He only accomplished that the world started spinning. The ground was moving and for a moment Castiel was sure although already sitting he would fall down face first on the pavement.
There were voices near, frantic foot steps. Then Dean and Sam were suddenly crouching next to him. Castiel was not able to understand all of their words, his blood rushing loudly in his ears, the world around somehow covered with a strange grey fog that threatened to swallow each and everything – except the pain.
"Take it easy, take it easy, all right?"
Although his senses were dulled the Angel could hear the worry in Dean's voice quite clearly. The pressure inside his brain was spiking up every time he moved, blurring his vision, leaving him dazed for a few seconds as his friend tried to pull him in a more stable position. Still he had to reassure both hunters. They had a purpose, the reason for them being here was not to comfort Castiel but to make sure their parents survived for themselves to be born. He himself was expendable.
"Fine..." The Angel sounded breathless, voice raw and strained. He tried to target his rolling eyes on Dean who was currently crouching in front of him. It was harder than expected and produced a new wave of nausea and vertigo. Luckily this time both Winchesters helt him in a tight grip so just his head lolled a bit to the side. "... much better than I expected..." No, talking was not good. A sharp pain cut through his brain, down to his chest, splitting his torso in two halves, leaving him unable to breath. The world around darkened noticeable. There was something inside his mouth, coppery liquid. "This his how blood tastes," a part of his brain stated before something cold rushed through his head, spreading rapidly through his entire body, leaving him numb while darkness swallowed the world around. The last thing he felt were strong hands holding him up and Sam frantically saying his name. "This is how unconsciousness feels," then only blissful darkness.
~*~
As Sam helped his brother hoisting up the limp Angel Castiel's last words echoed through his mind. "...much better than expected..." So he had not planed on surviving this little trip. He wondered what else the Angel had conveniently forgotten to tell them – and what they were supposed to do now. They had no money, no car, not even a motel room but an unconscious, bleeding Angel. What would Doc Brown have done?