Chains engraved with angel warding shackled Casiel as she awoke, alone in a freezing cell.

She sits up slowly, grasping her head, finding blood. Where was the blood from?

Her healing ability had been compromised.

She rests against the concrete wall beside the stone hard bed, looking intently at the mirror which would of course be a disguised window. She didn't bother screaming, or asking for help.

'Whatever I did, whatever happened, this is what must be done.'

///

"That is completely cruel" Sam Wilson cringes, staring into Casiel's cell, watching as she bounced a handball she'd summoned from seemingly the air.

"General Ross, you cannot keep her in there!" Tony growled, "it's completely inhumane and immoral-"

"She caused immense damage to the city and was deemed a considerable threat to human lives."

"This is bullsh!t" Barton snapped suddenly.

"She's not a monster, she's a child" Loki added cautiously.

"CHILDREN do not level sections of cities!" General Ross snarled.

"You know she can hear you, right" Balthazar interrupted, pacing around outside her cell.

"How the hell would you kno-"

"I'm her biological brother, you pompous pri-"

"That's enough" Steve interrupts, frowning. "This is inhumane, General Ross"

"Well, good thing she's not human" He spits.

Thor and Carol, who had remained silently resentful, both resist the urge to lunge at him, resorting to holding each other back.

Soon after his abrupt exit, the TV in Casiel's cell switches on, she's forced to watched the carnage the Guardian had created.

The Avengers could no longer watch, one by one filing out of the room into the common area, sitting heavily on the seats, wordless.

"We can't let her stay in there" Scott murmured softly, glancing over to when Bruce was being led away to the medical ward, unable to breathe through his bruised throat. "I can't imagine how poor Banner is feeling."

"For now, we can't do anything but wait" Steve murmured softly, defeated.

"I say we bust her out of here in a mighty display" Thor boomed.

"Or we need to prove her allegiance" Bucky suddenly chimed, sitting up. "General Ross said this used to be a training facility, right? Cas is one of the best fighters around."

"She still has those cuffs on her, she'll be weakened" Balthazar rubs the back of his neck.

"Where is she! You can't lock her up like she's a monster!!" Morgan yells angrily, cutting through the conversation.

"Yeah, mongrels! That's our best friend!" Kara snapped, eyes shimmering green.

"General Ross has instructed that she remains detained-"

"Send him to us and see how goddamn brave he is" Luke growled, hands flaming.

"Kids" Steve called calmly, "come here, please."

Wordlessly, they glare ferociously at the guard before making there way to sit. Carol rests her arm on Kara's shoulders, Scott gently pats Luke's back, Thor allowed Rachel to sit on the arm of his chair and Morgan sought a hug from her Dad, who stood proudly at her strong desire for justice.

The team had been defeated by the most harmless enemy they had ever faced.

Corruption.

///

Over two weeks and movement to a much larger detainment area, the Avengers had come to visit Casiel each day. They would come and converse with her, bringing her little games and DVD's to make her detainment ever so slightly easier.

Bruce still hadn't been to visit her, recovering. Little to her knowledge, he also wasn't allowed to.

Loki had often visited during the day, sitting in the book corner of her cell, reading to her, calming her.

Bucky has visited at lunch time each day, playing handball with her.

Carol had come and sat with her, telling her all of the adventures she'd had. In return, Casiel would tell her a story from her past, too.

Scott would sneak in cookies and sweets for her, and showing how his ants performed tricks.

Peter came every day after College, often playing board games with her.

Tony had come with old suits, allowing Casiel to tinker with them.

Kara came and watched movies with her.

Luke came and filled her in on school.

Rachel made sure Casiel didn't lack in exercise, often training each other through boxing or handball.

Morgan brought Casiel's most recent project, a small robot, in each time so they could tinker together.

Vision spent many nights when Casiel couldn't sleep playing chess with her.

Despite all of the support and love from her team, her family, she felt nothing but fear when they weren't around.

Casiel is an ancient angel. Being powerless with engraved titanium angel-warded bracelets on her wrists, making her virtually human, terrified her. She knew a lot about humanity but not how to be a functional human being. During her chess matches, Vision would explain to her all the human habits he'd picked up from living with Wanda, which reassured Casiel that she could adapt just like he did.

When Casiel would finally collapse from exhaustion on her bed, Vision would quietly rest the blanket over her and exit through the far left wall.

"General Ross" Vision spoke calmly, despite being startled to see him on the other side of the glass.

"Apparently detainment of this magnitude cannot he continued" was all Ross spat. "She will be allowed out, but with the bracelets on."

"With all due respect sir, suppressing her power-"

"Vision, it's better than the cell" Tony spoke gently, catching an eye roll from Steve. "At least she'll be at home, with us." Vision nodded in agreement.

"When can she leave?" Steve pursues.

"When she affirms her allegiance. She needs to prove herself worthy."

"So what, an obstacle course?" Bucky snickered.

"This building is a former training facility. We will utilise this to our advantage. Let's see how she does under pressure"

"Testing her allegiance is ridiculous, it's Cas" Tony frowned, trust unfaltering.

"It's the only way I'll sign her off for release," Ross claps his hands loudly, "now, let's see how tough she can be."