A/N: So this takes place sometime after they return from Apocalypse world. So spoilers for the end of season 13/ I've also changed things.
Castiel in Pieces
Prologue
Castiel couldn't believe how different the other world was from their own. Apocalypse world as the Winchesters had referred to it as. They were out in the search for Charlie and Ketch who had been captured by the angels. Cas felt a quick shutter go through his body. The thought of his kind decimating this world made him ill. He let out a small sigh, though the refugees trusted Jack (Cas figured it was because he had been helping them) But Cas felt like they didn't trust him, they glared at him and Gabriel and Lucifer (though Lucifer was Lucifer so that probably was why) He clinched his fists he wanted to help these humans, he felt almost at fault even though it wasn't he or his brothers and sisters actions. He took a sharp breath as he seen another version of himself heading right towards him.
Nothing was as disturbing as another version of himself coming at him. He shook his head, bad enough the creature in the Empty looked like him now here he goes about to face down himself again. He cornered the other Castiel who let out a very undignified yelp. Cas made a mental note to ask Dean if he's yelps sound that… girly.
The other world Castiel held up his hands and looked at him. Shock was clear across his face he didn't expect to see another him either. "Wait no!" He screamed with a strange accent as Cas drew out his angel blade. "Please don't we are the same."
Cas felt his eyes narrow out of annoyance. "We are nothing alike."
The other Castiel stared at him and a small smirk played across his face. "No? Maybe I should find out?"
Before Cas could move the other version of himself laid his fingers on his forehead. Cas felt a brief flash of pain, he plunged his blade into the alternate version of himself who let out a scream and hit the floor. He glared at the fallen Cas his head pounded as he looked down at him.
"Cas!" Dean called. "Are you okay?" he asked he was right by his side his hand on his shoulder.
He gave him a nod. "I think so… just didn't think I would," He pointed at the other Castiel. "Have to kill myself."
Dean rubbed his back lightly. "I'm sure it's weird." He pulled him into a hug. "At least you dealt with him…"
Cas could tell by Dean's tone that he meant he wouldn't have been able to do it. "Yeah Dean but he wasn't me... he spoke with some weird accent." He felt a brief surge of pain in his head and he flinched, exhaustion creeped up on him and he fought it back. He could be tired once they got back to the Bunker.
Dean looked around and placed a small kiss on Cas's head. "Are you sure you're okay?"
He gave a small nod. "I'm fine let's just go. We got to get out of here before the portal closes."
They headed back to the base which was Bobby's salvage yard with Ketch and Charlie in tow. Cas had put the whole incident with the alternate him behind him; little did he know that, that incident would change him.