The Angels Threat

Seraph

"What are you doing, boy!" John roared as the stared at the Winchester and the angel laying naked on the motel room bed. Dean just stared in shock at his father who seemed to have risen from the dead, a natural occurrence in the family. "D-dad?" He stuttered, scrambling to pull on his trousers.

Johns eyes were a pair of blazing fires as he stormed forward and rammed Dean into the wall, hard. Not even shocked that he was alive once again, he had other things on his mind now.
 "All your childhood," He took a deep breath, drawing down the unhidden fury. "I taught you to kill the monsters that hid in the dark. Now your having sex with one!" His hand at Dean's neck now, cutting off the air supply.
 "Cas isn't a monster-" Dean tried to reason with him but all he got in return was a punch to the cheek, he could feel it swell immediately and he tasted copper in his mouth. Blood; he'd bitten into the inside of his mouth.

Dean didn't fight, this had happened once before. He was 17 and had joined his dad on a hunt. Killing a nest of vampires, easy enough. One of the vampires remained and Dean refused to kill him because he had asked for mercy; the vampire hadn't killed anyone, he had been force-fed human blood and turned into a monster.
 Dean had no reason to kill him.
 But John had decapitated him without a second thought and gave Dean the beating of a lifetime when they had returned to the motel room they had set up base in.

But this one was going to be more brutal than the last. He could practically sense it. That was until John's hand was stopped mid-punch by Castiel.

John was abruptly spun around and pinned to the floor with Cas' index and middle finger pressed against his temple. Neither dared to move. Cas was going to smite him.
 "Cas..." Dean said, his voice wavering a little. "Cas, move your hand."
 Castiel didn't move, his eyes were dark and the shadows that fell over his face were unnerving and... Deadly.
 He just spoke through gritted teeth.
 "Consider this the first and last warning you get. You hurt Dean Winchester again and I will smite you like i have done to every creature before."

This wasn't the normal Cas, this was the warrior, the seraph. The one who listened to the orders of heaven and despised humans for their weakness. It was as if Cas had never left heaven.

They all stayed where they were for a few more tense seconds until Cas finally moved his hand, time seemed to flow properly and everyone seemed to start breathing again. Dean's heart was hammering against his rib cage. John's eyes were wide and full of hatred, his hand rested on his gun, ready to draw at any moment.
 "Dean is under my protection." Cas finally said, his voice hollow, he didn't raise his head. "You hurt him. I kill you."