This was inspired by a post by lovingsmutandfluffdeactivated2 on tumblr. (I saw the post on Pinterest) He or she wrote a small paragraph and that inspired this. Enjoy!

He couldn't take it anymore. He couldn't look at that… thing that once used to be his brother. The black eyes were too much. That smirk was too wicked. Those words were too truthful to be right. He knew it was the demon talking through his brother's lips.

Demon.

Dean wasn't possessed. There wasn't something crammed inside his brother's body that controlled what was said and done. There was nothing in there. Only Dean. Dean was the demon.

Every word that spilled out of his mouth was the bitter, venomous truth that he had been able to contain for years, but now he had no filter, no dam. Dean knew he no longer cared about his brother's reaction. He embraced that broken dam. Let his brother hear the truth for once. His little brother's shattered heart was another game to him. It was a relief, a breath of fresh air.

Sam couldn't take the truth... even though for years he knew it to be true. He just never thought he would hear it from Dean.

Sam left the room with Dean still tied to the chair. He walked through the corridors, pacing up and down empty hallways, wandering without paying attention to exactly where he was going. The quiet was nice, to get away from Dean's words and his screams, but the words and the screams still echoed in Sam's mind.

Without realizing, he found himself in Dean's room. He sighed as he walked inside. The note that Dean had left still laid on the pillow. Sammy, let me go. Picture frames were neatly placed on the nightstand and table. The bright faces of young Sam and Dean looked back at him. John smiled in one, but the one that held his attention the longest was the picture of his mother and a very young Dean. He grinned as he picked up the picture, examining every inch of the photo before sitting it back in its place.

While he continued to look at his brother's small collection of photos, Sam heard the scraping of shoes on the cement floor. He turned around and right behind him was Dean with black eyes, holding a rusty wrench.

"Heya, Sammy."

Dean swung the wrench, and before he could react, Sam heard a loud crack and felt a sharp, splitting pain.

Everything went black.

When he woke up, all Sam could feel was his skull. He felt like he was in the middle of five hangovers; the world was spinning, and his vision pulsed with flashes of light. A firm hand shook his shoulder gently.

"Sammy, wake up." Dean.

As his vision cleared, he saw that Dean was standing over him with a unconvincing concerned expression upon his face. "Wake up, sunshine." He grinned widely as he stood up straight. Sam noticed he was gripping tightly to a long knife. "Mornin."

"Dean," said Sam hoarsely. He pulled but his arms and legs were tied to the chair.

"Ya know, you are one heavy son of a bitch." He paced slowly around Sam. "Took a lot to drag your ass down here." Sam looked around and finally noticed he was tied to the chair that Dean was tied to.

"How did you get out?"

"'Cause you, my brother, pumped me so full of blood, I became human. Not all the way human, of course, but enough to get out of those chains and devil's trap." He continued to walk slowly around the chair. "Did you not realize what the hell you were doin'. Come on, Sammy, you're supposed to be the smart one."

Sam shook his head. "Dean, let me go. Please."

"'Dean, let me go,'" Dean mocked. "Please! I told you before, if you would have let me go, none of this would have happened. I was happy without you!"

"Dean." Sam struggled at the ropes that kept him in place.

"Shut up!" shouted Dean. He smiled and laughed. "There's no getting out of this one, Sammy."

He raised the knife to his arm, using his fingers to pull back his sleeve. He slid the knife across his arm and dark crimson blood oozed from the wound. The rich, salty smell filled the air. But it didn't smell like ordinary blood to Sam. It was sweet.

Dean looked up at Sam with a smile and black eyes. "Remember this."

Sam shifted the chair. "Dean, no."

"YES." They both watched as the blood ran down Dean's arm.

Sam wasn't thirsty. Hadn't been for years, but he knew if he got just one taste, it would all be over.

"I'm gonna to make you addicted again." He stepped forward, arm held out for Sam to see. "I want to see that thirst of yours. Drink 'til your eyes are black. You're gonna be the ruler of Hell you were destined to be, Sammy. The King of Hell, the real King. And I'll be your knight. We can rule Hell. Together."

Sam began to pull at the ropes even though they were burning wounds into his flesh. "Dean! Stop!"

Dean rushed up to Sam, pushing his bloody arm against Sam's face. "Bottoms up, brother." He held Sam's head in his other hand, pushing his face closer to the blood. Sam pulled away but couldn't move more than a few inches before Dean would push him back. He tightly clamped his mouth closed as he tried to pull his face away from Dean's arm. "Come on, we can be together. Isn't that what you want?"

The iron smell was overwhelming, the warm liquid smeared onto his face. It flowed like rivers down his cheeks and into his hair.

Just keep your mouth closed. Just keep fighting.

...

Cas walked into the bunker. The library was empty. He continued through the halls looking into every room until the only room he hadn't checked was the dungeon. He came to the room and found the door was already cracked open. He pushed the door open and walked in. Sam stood in the center of the room, just outside of the devil's trap. The chair in front of him was empty, the ropes torn. Pools of blood were spread all across the floor all around the chair.

"Sam?" said Cas with his husky voice. "Where's Dean?"

"He got away," answered Sam without turning around. "He was able to get out of the trap and attacked me. He… got away."

Cas began to make sense of what Sam was saying. "He became human enough to get out." Sam nodded. "Damn it."

Slowly, Sam turned around with his face to the floor.

"Sam? Are you okay?" asked Cas.

Sam looked up. A smile spread across his face.

His eyes were solid black.

"Never better, Cas. Never better."