The thing with bad news, Castiel reflected, is that there's just no good way to say it.
The garage door squeaked as Bobby and Mary returned to the Bunker. They were going to be in the all-but-empty main room in less than a minute. They would have questions, questions that Cas wasn't sure how to even begin to answer.
What was he going to tell them? The angel raked his hands through his hair, a human habit picked up from the Winchester brothers. He wasn't sure he had the strength to admit that, once again, he had failed so catastrophically that the very world might be forfeit. Of all the languages Castiel knew, none of them were quite capable of fully expressing the enormity of his negligence.
"Cas!" Mary's hands were on his face, his shoulders, looking for injuries. There weren't any. It felt wrong to have lost such an important battle without any wounds to signify his utter defeat.
"Cas, where are they?" There was a hint of panic in her voice. Castiel could tell that she feared for her children's lives. How was he supposed to tell her that death was preferable to what they were currently enduring? Sam was once again at the mercy of Lucifer's unbridled wrath, Jack was suffering from having his grace torn from him, and Dean…
Castiel was intimately familiar with possession. He knew exactly what it meant to say 'yes' to an archangel. He knew what sort of power that simple word of consent gave the possessor, and what kind of toll it took, mentally, physically, and spiritually, on the possessee. He knew exactly what it felt like to have your body's control ripped away by a being infinitely more powerful than yourself, to be helpless in your own skin as your hands destroyed everything you held most dear. He knew how impossible it was to even endure such a violation, much less manage to gather the enormous strength it took to wrest control from your abuser for even a moment.
"Cas? What happened?" Mary begged. He owed it to her to explain. She was Dean's mother: she should hear it from someone who cared, someone who understood. She had promised her son that angels were watching over him, and Castiel was that guardian angel. A terrible one, but one nevertheless. He had failed Dean, again, and in doing so had failed her. Again. She deserved to know that. He opened his mouth to voice his own condemnation, but the words wouldn't come. Or rather, he opened Jimmy Novak's mouth, and almost vomited because of the reviling revelation that he was no better than the monster currently desecrating Dean's body even now. Angels were parasites, unable to live in this world without utterly destroying the very beings they were designed to protect.
He was startled from his self-flagellation by Sam's voice whispering through his head. "Cas? I'm not sure you're still listening to Angel Radio, but if you are… Michael won and Lucifer is dead and Dean… Dean lost." Cas winced as Sam bit back a strangled sob. "Jack and I are headed back to the Bunker. Call in Rowena and Charlie and Ketch and all the others. Take care of Mom."
Castiel bowed his head. Thankfully Lucifer was dead at last, but at what cost? And how was he supposed to take care of Mary when he was still reeling?
"Cas, you're scaring me," Mary whispered. Her hand brushed gently across his cheek. Cas pulled away. He didn't deserve her care, her love. Not after what he'd done to her sons. He was surprised to see her fingertips glisten with tears when he opened his eyes.
"Sam and Jack are alive," Cas forced the words past unwilling lips. He had to be strong. Strong like Dean was... is always strong. If he'd learned nothing else from the Winchesters, it was how to keep playing through the pain. "They're returning to the Bunker as we speak. Lucifer is dead." Mary's shoulders slumped with relief as she processed the good news.
"That's great and all, and we can throw a party later, but where'd they go that they need returnin' from? And what about Dean? What aren't you tellin' us, boy?" Bobby snapped. Cas almost smiled. It was such a Bobby thing to say that he could almost forget that this wasn't their Bobby. Their Bobby was dead, killed by the monsters Castiel had unleashed in his hubris. Yet another failure on his very long and horrifyingly impressive list of failures.
"Lucifer took Sam and Jack," he croaked out the words with a throat that was too tight. "I don't know where, and we couldn't follow," Cas twisted his hands together. He felt the loss of his wings acutely. If he'd been able to fly then maybe… but he couldn't. Not anymore, and he only had his own mistakes to blame for that. Castiel explained what had happened during the brief fight: Michael's vessel damaged beyond repair, Jack's grace taken, Dean left desperate for any way to save his brother.
"Michael needed a new vessel if he was to have a chance at killing Lucifer," his voice sounded ragged even to his own ears. "Dean needed a way to save Sam and Jack. So he said 'yes'."
After everything, despite everything, regardless of everything, Dean had said 'yes'. For all their talk of free will, there were apparently some fates that even Winchesters couldn't escape. They could only be delayed, and maybe sometimes that was enough. What that meant for Castiel, who had sacrificed everything to keep this very thing from happening was anyone's guess.
"Dean is possessed by Michael?" Mary said slowly, desperately trying to understand. "But doesn't Michael…"
"Want to destroy the planet? Again," Bobby growled. "That ijit."
"We can fix this, right?" Mary looked at Castiel, hope fragile in her eyes. "Sam and Jack are alive and we can fix this together, right?"
Cas knew this cue. This was when Dean would smile disarmingly and clap them on the back and promise them the impossible.
He wasn't Dean though. Dean was gone, quite probably forever. Cas wanted nothing more than to just close his eyes and fall back into the oblivion of the Empty. But Sam had asked him to take care of his mother, and Castiel couldn't bear the thought of one more failure. Not today.
"We'll figure it out," he spoke the well-worn promise with what little confidence he could muster. "We always do."