coda to "The Man Who Would be King"
Castiel remembered Cain and Abel. He had seen Cain grab a stone the size of a fist and bludgeon Abel to death, Cain’s face contorted in hatred and jealousy. He had seen Cain cover up the evidence of Abel’s body with dirt but not realize that the smell of blood and murder stained the air and ground. He had seen the lack of remorse on Cain’s face as he dared to lie to God and Castiel had not understood.
“Why did Cain murder his own brother? Why does he possess such hatred?” Castiel had asked Uriel.
Uriel had sneered. “Because they have free will, Castiel. Give them free will and they will always turn on each other.”
Castiel had not truly understood, but he had accepted it.
He knew differently now. Evil and grief had followed Dean and Sam for their entire lives, serving as obstacles as wide as oceans. Dean and Sam had fought against their supposed destinies their entire lives and had always found a way back to each other. Free will could be beautiful and incredible. Dean and Sam proved that.
Castiel still doubted whether he deserved free will, but he knew that he would do anything to protect Dean and Sam’s, even if his morality was a casualty.
He only hoped that they would forgive him in the end.