Gabriel charged at Cas first, his angel blade slicing a tiny hint of his neck as Castiel tried desperately to hold back the force. It's harder for an angel to heal themselves from an angel blade attack, so the wounds on Gabriel weren't fully healed. Castiel picked at the gnash in his arm, cringing when his brother screamed. The two drew back, wings towering over them. Gabriel's wings were a dark black as they trembled in a crooked manor over his body. His eyes twitched before he went in for another blow, managing to cut Castiel's wrist as he held it up in defense.
Castiel gritted his teeth, he didn't want to fight with his brother, but there was no way in hell he'd let him get to Dean. "Stop this please!"
"What's the matter Cassie?" Gabriel's smile was twisted. "Scared you'll lose?"
"You're not yourself!"
"No shit!" Gabriel flung backwards as Castiel pushed, slamming into the wall with force enough to crack it.
"What happened to you brother?" Castiel stood his ground, but gave a look of pity.
"What happened to me was a miracle! No, better!" Gabriel shrieked right before charging Cas once more.
This time he used the back end of his blade, popping it on Castiel's skull. "No soul brother. I guess humans aren't the only ones who can block it all out. I'm so much more powerful!" Gabriel knocked his brother hard, off his feet and to the ground. "Sentiment just holds you back."
Gabriel pinned Cas's arms above his head with one hand, using the other to scrape the tip of his blade along his brother's skin. His grin never faded, but continued to widen. An angel's soul is what steadies their grace, like a harness. When they loose that, the grace inside becomes cold and dark. The power takes over. The angel holding him down, threatening to kill Dean, scraping his skin with the angel blade... that wasn't his brother Gabriel. It was something new and dark possessing his body. Power, a beast. Inside Gabriel was pure, unbridled power, and it was a scary thing.
Castiel whimpered with pain as the blade dug into his shoulder. That's when the evil smile brightened the slightest bit. A cruel idea popped into the beast's head. It flipped Castiel over onto his stomach, still pinning him violently to the floor. The angel blade glistened as it ran along the root of his wings. "Gabriel!"
The blade dug into the roots, painfully chopping through it's muscle. Feathers flew everywhere as Castiel's wings flapped around desperately. He screamed. Castiel screamed the scream of an angel. The one that could be heard by all angels and now, by Dean.
Dean was immediately woken from his sleep. He could hear his name being called. It was another angel scream. He felt hell, he grabbed at his ears writhing with pain. "Stop it!" he screamed. "Stop it now! Stop! Please!"
Gabriel cut at the wing's nerve, but it didn't want to be cut. So he pulled it. Gabriel yanked the wing straight out from Castiel's back. The sound of flesh tearing and a sudden pop was enough to make even him cringe. Castiel's screaming turned into crying.
"Stop it! Just stop it!" Dean begged, "Please stop it!" He fell to the floor, cupping at his ears.
"Dean!" Castiel cried. "Dean!"
"Cas!"