The pain is losing some of its teeth now. Tony finds that if he pushes through the worst of it first thing each morning it's not long before it takes a back seat to the punishing regime he sets himself. The painkillers sure help. And having something else to focus his mind on.

What he's not getting used to is his useless left hand.

No matter how many times he does it, no matter how many times he jars himself or breaks his own concentration, he just can't seem to keep it in his head not to reach out for that tool. Or move to steady something. Or scratch his nose. The sling thwarts him every time, and the injury flares up as though he needs the additional reminder of his condition. His frustration with himself is steadily building, and combined with a significantly reduced work rate, the constant ache and the lingering fatigue, his mood is souring by the hour. He's entirely aware of it. That doesn't make it any easier to control.

The third time he fumbles the pick he's using he throws it to the ground with a heartfelt "Goddammit!"

He presses his fingertips to his eyes for a moment and just breathes. He senses rather than hears Loki move to approach the work station Tony's perched at, his near silent footfalls padding to a stop at his back. Without opening his eyes to face any (admittedly well-deserved) judgement for his outburst, Tony holds out his hand with a forceful sigh.

Loki drops the tool into Tony's waiting palm without a word, his calm silence all the rebuke needed.

"Don't even say it," Tony grumbles, which is unfair and he knows it; Loki has been the very picture of patience with him these last few days.

"I wouldn't dream of doing anything of the sort." There's the ghost of amusement in his voice despite this statement. He moves away again, respecting Tony's space, and returns to the workbench he's commandeered for himself and from which he observes Tony at work.

Tony's trying not to dwell on just how invested Loki seems to be in doing this thing, to the point where he'll put up with being Tony's dogsbody around the lab and apparently now his babysitter too. He's also taking a genuine interest in Tony's process, although how much of that is to reassure himself nothing untoward is being prepared for him Tony wouldn't like to guess. Tony's doing his best to be transparent about what he's doing just in case, and even if he's not used to having an audience he's found it occasionally helpful to have someone to bounce ideas off of. It's sure going a good way towards alleviating some of the guilt he's already building up about this, and that's before they've even started trialling it.

Reverse engineering is not really his gig. Sure, he's taken plenty of things apart in his time. Put a good deal of them back together again, too. There's something quietly reassuring about reconstructing the tried and tested, slotting everything back in its place just where it should be. When the design is flawless and the artistry apparent, every engine, every piston, every carefully thought out circuit can be a thing of beauty.

But riding someone else's coat tails has always felt a bit like cheating, and if he's honest it's never held the same appeal for him as the pure satisfaction of creation. Of putting something together from scratch. Of shaping something with an innate, organic instinct for the correct direction. Of giving the inanimate life. He's also never been very good at following someone else's lead.

Tony is first and foremost an inventor, after all.

And anyway, this is different.

Leaving aside the ugliness of the tech, its poor construction and its even uglier purpose, his mind is always several steps ahead. He doesn't want to think this way, but he can feel himself automatically scoping out new ways to improve on it. He's thinking through all the circuits he would change, identifying all the inefficiencies and basic streamlining its architect had missed, criticising its flaws and devising the solutions.

He despises being required to put himself in the same mindset as whoever came up with this twisted piece of shit.

He'd picked it apart pretty easily. The inner workings weren't that hard to decipher. But the cruelty of the thing, the way it's designed to dig into someone's flesh and cling there like a parasite, the insidious tendrils of energy it emits, the agony and paralysis it causes… He hates it. It turns his stomach. Decoupling those design traits from the one he actually needs is proving a more difficult task than he'd hoped.

He's starting to suspect there may be no way to make this thing painless.

He'd offered to work on something to help with that. Loki had refused him point blank. He'd insisted he needed his wits about him if he was to gain anything from this, but Tony thinks he knows better. The prospect of being drugged again had clearly terrified him.

Apparently prolonged and unmitigated agony is by far the preferred option.

Tony doesn't want to think about this. It's not helping. Maybe some time away from the lab would be a good idea.

"I want ice cream," he announces when he's got himself under control. "You want ice cream?"

Loki looks up at him, one perfectly groomed eyebrow raised, and Tony casts him a mischievous smile.

"Enable me already," Tony commands and hops off his perch.

"Whatcha reading?"

Loki spins the tablet round on the counter top so that Tony can see it. An open access journal lists a number of papers discussing known enhanced individuals, speculation on their origins, and the ethical use and governance of those with supernatural abilities. Tony makes a neutral 'huh' sound and pushes it back, going in for another spoonful of dairy-free chocolate fudge.

Loki had complained to him previously about the lack of information available online concerning the… more mystical end of the scientific spectrum. He'd been disappointed to be informed that other than he and Wanda, documented examples of abilities like his were not exactly commonplace. Looks like he's delving instead into Accords territory, and Tony finds he's actually interested to know what Loki makes of it.

"Find anything interesting?"

"Only more questions. I'm beginning to wonder just what one stands to gain by openly declaring one's… talents."

Is that a reference to Tony outing himself all those years ago? Or just an observation related to the breakup of the Avengers? Either way, the guy's done his research, and Tony's getting the distinct impression he's being mined for information. Touché, Tony thinks.

"Guess it's more a question of what you stand to lose if you don't," Tony counters with. Or what it's possible to become without anything to keep you in check, he doesn't add.

Tony's caught Loki on YouTube plenty of times, scouring for footage of New York. Analysing every image, report and article he can find. He's not sure it can be doing the guy's mindset much good, but even aside from making it obvious he's sticking his nose in where it doesn't belong, there's not exactly much Tony can do to stop him. He admits the curiosity would be killing him, too.

He wonders what Loki sees when he looks at those.

Loki regards him thoughtfully. "You do not regret choosing the life you lead?"

"You mean going public? Not really. Sometimes, maybe. Using my position for the greater good? Not even a little bit. Because I've been on the other side of that fence. Hell, I lived that life for longer than I've been Iron Man. And let me tell you - this whole deal may suck sometimes, but I would never go back to that."

The sad smile Loki gives him is hard to look at. "So you've not always been the celebrated hero I've read so much about."

"Not even close. Not sure I even know what that word means, anyway."

This doesn't seem to deter Loki any. "But you were never really the 'bad guy'. You've never murdered people."

Tony hides his reaction to that behind another spoonful of ice cream. This conversation is rapidly taking a direction Tony is not prepared for, and he's almost sorry to have left the relatively straightforward consent-and-dubiousness-thereof minefield waiting for them in the basement. "That probably depends on who you ask. It's all a matter of perspective."

Loki frowns at this and looks away, apparently unhappy with this answer. Whether that's because he doesn't believe Tony could have such a shady past or because he's unwilling to allow Tony to draw parallels between their situations it's difficult to know.

He sure as hell isn't qualified for this, and therapy has never been something Tony's put a whole lot of faith in (for himself at least), but something in him is insisting on seeing this through. "Look, no one can change the past. All you can do is learn from your mistakes and try to be better when you can. You know-" he tries a self-depreciating smile, "-to make a difference and all that."

Loki sighs heavily, pushing his half-eaten bowl of dessert away. "You make it all sound so simple."

"Really? Because it isn't. Take it from me. And I'm probably the last person who should be talking about any of this stuff. Just ask Rhodey. He'd tell you all kinds of unflattering stories from the good ole days, no questions asked."

"I think you do your friend a disservice."

Tony laughs softly. "Yeah, you're probably right. You didn't hear this from me, but he was always the best part of Tony Stark, back in the day. Kept me from straying too far from the straight and narrow. Still does."

"You credit Colonel Rhodes with shaping your own nature for the better?"

Kinda a weird way to put it, but... "Well sure. Isn't that what friends are for?"

The silence that follows sounds suspiciously like I wouldn't know to Tony's ears. Uncomfortable in a way he can't quite put his finger on, he decides to bring them both back to the issue at hand. "So listen. You still sure about all this? You really want to do this?"

"I grow tired of hiding in the shadows of my own mind. And if we are truly to fear the threat you and the colonel seem to believe hangs over us, I would sooner have any means at our disposal ready to act in our defence than to be caught unprepared. Wouldn't you agree?"

Tony doesn't comment on the use of the word 'our', and he hopes the smile pulling at his mouth hasn't given him away.

"It's gonna hurt though. You get that, right?"

Loki's own smile is grim. "What is a bit more pain when it will be mine to control?"

"Last chance. We can go back to the drawing board, figure out something else. Maybe wait this thing out a little longer and give Wanda another try. There's absolutely no pressure from this end, I just want that to be clear."

Loki simply looks at him and holds out his hand.

Tony clutches the tech to his chest like he's being asked to hand over the keys to his favourite ride. "I want it on the record that I object to this and everything it stands for. I really, really think it's a bad idea." They've been over this, but Tony'll be damned if he doesn't give just one more token protest.

"I assure you, Stark," Loki says with that special brand of condescension he's made his own, "I will not hold you responsible for what may transpire. This has been as much my idea as it has been yours. I am perfectly able to withstand some discomfort."

And isn't that just the problem.

Reluctant and determined to let it be known, Tony hands the tech over with a last unhappy frown. He watches Loki examine it with an almost serene interest.

They've gone for a hand-held design, something Loki can activate and release on command. They'd both agreed that something as far from the original as possible was the preferred way to go, and something Loki could have full control over had been a deal-breaker Tony hadn't even thought to challenge. This new design should also act as something of a dead man's switch if it should come to that - not something Tony had invited Loki's input on given it would have been non-negotiable, but something that's helping him sleep a little better at night. He just hopes it's a contingency they won't need.

This could still go all kinds of wrong.

"Okay," Tony says, turning to gather the monitoring equipment he needs, "this is just a test run. We're gonna take things real slow and dialled right down. Lemme just-"

Loki, crazy masochist that he is, doesn't wait for Tony to finish speaking. He plunges a thumb down on the activator and goes rigid as the current is triggered.

Tony can't prevent a fuck from escaping as he scrambles for his screen, and by the time he's punched in the right codes to bring the readouts up Loki has already disengaged the device. He counters Tony's look of horror with a humourless grin.

"What is wrong with you?" Tony barks at him, not at all impressed.

"You are holding back," Loki observes calmly. "Increase the power."

"Do you not listen to a word- I just said we're testing it first."

"I have just tested it. It is not strong enough."

"Because we're taking it slow. I don't want to have to peel you off the floor by rushing this thing. If I had my way we'd be waiting for Vision but someone insisted we start early."

"I am not made of glass, Stark," Loki says, a hint of impatience creeping into his tone. "I am not fragile, or feeble. And if you think I want to prolong this any further than necessary simply because you cannot stomach doing what must be done-"

"Alright alright. Jeez. Keep your panties on."

This is not cool. This is beyond not cool. He's got a bad feeling about this and he's pretty sure Rhodey is going to chew him out when he finds out about the stupid risks they're taking here, but there's something about the way Loki is looking at him that is making it hard to argue.

This is a choice - Loki's choice - and he wants to respect that. He wants to let the guy have some agency for once. He just wishes it didn't have to be at the expense of Loki's physical wellbeing (and Tony's thrumming nerves).

"Taking it up twenty percent," Tony accedes, and when Loki stares back at him balefully he repeats himself with emphasis on the 'twenty'.

Loki doesn't even finish rolling his eyes before he's plunging the switch again, and this time his expression tightens just a little. Tony nods at the feedback on his monitor and tries to focus on the peaks and troughs of the data being received. Okay, this he can work with.

Again Loki disengages the tech, a little breathless but otherwise unharmed.

"That's good," Tony hurries to assure him. "We're running some decent numbers here. Here, take a look."

Perhaps he should have anticipated what happens next.

One moment Loki is leaning to scan the readouts with a feigned, casual interest, and the next he's plucking the display from Tony's hand with deft fingers.

Tony only manages an indignant "Hey!" before Loki is manipulating the controls, hiding what he's doing from Tony's view with his broad shoulders turned. Loki easily evades Tony's snatch when he tries to reclaim it, and still injured as he is, Tony isn't fast enough to try a second time.

When Loki activates the device again he curls in on himself with a gasp of pain. He falls to his knees, his whole body trembling and his eyes screwed shut, and clutches both the tablet and the switch in hands made claw-like with the effort.

"Loki, goddammit, stop!"

Even if Tony had both hands at his disposal, trying to prise Loki's grip open would have been an exercise in futility. He still gives it a try, and when that doesn't work he shakes Loki's shoulder with an entirely unfounded threat to kick his ass if he doesn't stop what he's doing right now.

He lets five more seconds of this shitshow pass before he plays his last card. "FRIDAY, override!"

Loki sags with a gasping breath and Tony has to lean into him to keep him upright.

"Why... did you… stop…"

Tony has to bite back some choice insults that he figures wouldn't be all that helpful just now. "Take a guess, genius! What's the matter with you? You're gonna blow a fuse." Maybe not quite the right analogy, given that tripping a mystical circuit breaker is exactly what they're going for here, but Tony's not exactly thinking clearly right now.

"It was working. I could almost feel it…"

"Yeah? Well too bad. You're done."

"No…"

"Yep! I'm calling the shots from now on, so get used to it."

He's moving to take the tech from Loki's now slack fingers when a flickering at the corner of his eye brings him up short. The fabric at the right side of Loki's torso seems almost to be shifting, layer upon layer of half-formed images materialising and being overlaid in quick succession. When Loki notices he gazes down at himself in fascination, and when he meets Tony's eyes it's with a watery smile that looks too broken to be completely genuine.

"You see," he insists in a harsh whisper, the grin turning just a shade towards the manic now.

Tony doesn't like that look one bit. He's taking a breath to say just that when the expression falls away from Loki's face altogether. The stern lecture Tony's been building up to deserts him, replaced by something disturbingly like alarm.

"Okay?" he asks, trying and failing to persuade Loki's eyes to focus on him.

"Tired," Loki slurs before becoming a dead weight against the prop of Tony's arm.

Twisting to catch them both and not quite succeeding, Tony guides Loki to the floor as carefully as he can manage, cursing colourfully as he does. His healing ribs give a twinge of protest as they're required to support weight at an unnatural angle, and even sitting back on his heels prompts a flare of discomfort that suggests doing much more than this will invite some serious complaints.

With a sinking sense of realisation and not a small measure of dread, Tony wonders just how he's going to explain this to Rhodey and Vision.