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There. Second-floor window. We go in there. They'll never see us coming. Trust me. Now, weapons check. We're on the move in five.
Castiel’s hands began to shake as he approached the garden. The thunder and lighting had stopped a few minutes ago, but the silence was eerie. It was too silent. He clutched the handle of the gun tightly as he rounded the corner. He paused at the corner and looked down at himself. He was covered in the guts and blood of the Croats and his ankle was on fire with a burning, twisting pain that made it hard to move. He could feel blood dripping from his nose, mixing with the Croats and drying on his face. He took a breath and shuffled forward to the clearing. A loud cry tore through his lips and he rushed forward to the body lying on the ground.
“Dean,” his mouth formed the words as he felt his heart splitting into two. “You idiot, no no no, you idiot, don’t leave me, please.”
Cas fell to his knees and reached for Dean’s face, he paused and drew his hands back to wipe them on his equally filthy shirt. His hands shook harder as he felt for a pulse even though he knew it was in vain. Another sob forced its way out of his throat as he leaned over Dean, feeling tears drip down his face and staining Dean’s jacket. Taking a shaky breath, he laid down next to Dean. In that moment he decided to stay there. Castiel had no intention of leaving Dean’s side. He would stay there and wait for death, then he would see Dean again.
In the silence, he turned his head to look at the body next to him and whispered, “Don’t worry Dean. I’m not leaving. I’ll see you soon."
Hours passed, and Castiel remained there. At some point he had reached over to Dean and taken his hand, only to recoil at the cold, stiff, decidedly not-Dean feeling. He had simply closed his eyes again in a futile attempt to ignore the throbbing in his ankle when he heard the snap of a branch close to his head. Castiel didn’t even have the strength to move, he simply opened his eyes and stared blankly upwards.
“Lucifer.” His voice came out broken and cracked.
“Hello Castiel.” he said with a twisted smile on his face.
“Is this the part where you snap your fingers and I explode?” Cas choked out.
Lucifer feigned offense, “Really Cas, you think so little of me. It wounds me.”
Cas continued to stare at him blankly. Lucifer smirked again and crouched down to get closer to him. Cas looked away, toward Dean’s body.
“What do you want Lucifer, you’ve already taken the thing that means the most to me.” Cas whispered, more tears forming in his eyes.
Lucifer said nothing to him, but instead reached forward and placed two fingers on Castiel’s forehead. Cas jerked away from the touch when he felt the slither of twisted grace moving through him, but it was too late, he felt a burning sensation in the center of his head. He let out a scream and tried to break away from the blinding pain, but he was frozen in place. When the pain stopped, he recoiled from Lucifer’s hand and reached up to his head with trembling fingers, pushing hair away from the spot he had touched.
“This…” he trailed off.
A wicked gleam shot through Lucifers eyes, “The Mark of Cain.”
Castiel felt a moment of panic, “No. Lucifer you can’t—”
Lucifer turned on his heel and began walking away. “Have a good life Little Brother.”
Castiel’s panic turned to rage and he grabbed his gun, sat up, and began firing at Lucifer's retreating back. He screamed at him long after he disappeared. Eventually Cas stopped, his head drooped, and he once more knelt beside Dean. He would be cursed to walk the Earth forever, alone, searching for a way to rid himself of the curse. Alone. Without Dean.