Loki's voice is like cream, smooth and liquid. He murmurs enchantments, whispers promises and hisses threats, and Tony wants to just hear him speak forever. It isn't just his voice, though, beautiful as it is.
The sounds Loki makes are something that Tony knows he'll never get tired of. They're mostly on the same side nowadays and so he gets to hear the way Loki pants in exhaustion after a fight or a particularly hard spell or something unusually acrobatic. He gets to hear the growl of frustration Loki has perfected, the warm purr of a laugh as he mocks whatever he's fighting and even the sharp sounds of pain he makes when he's hurt.
The best part is later, behind closed doors. When it's finally quiet outside he gets to hear the soft sighs Loki breathes into the darkness when Tony runs his hands over every porcelain inch of him, checking for damage and reminding himself that they're both still alive. He loves the point when Loki's breath begins to pick up, quick and heavy and wanting.
Depending on his mood and the night and how tired they both are Loki will either clutch at him and gasp desperately as he moves, trying to draw him deeper, faster, or the trickster will writhe languidly beneath him and murmur quiet little moans, drawing it out until his voice takes on a ragged edge. Then he will finally come, arching beautifully, and Tony's name is always the cry torn out of him.
There is one thing that Loki cannot seem to help doing that turns Tony on more than anything. When they're in bed, when Loki is on top of him or below him or bent over something or knelt before him, he always trembles when he's close.
Tony can always tell when he's about to come, when he's pushing towards that edge, because a fine tremor will begin in Loki's bones, shaking him to the core. He will gasp and shake and lose the elegant control he has over himself, and Tony will grip his thigh or his wrists or his hips and feel the way his muscles tremble.
After he comes it takes a few minutes for the tremor to die away and Tony loves to hold him and feel it drain out of him. He will never mention it, though, because he knows that Loki would do everything in his power to find a way to stop it from happening if he points it out.
Loki moves with a fluid grace usually reserved for cats and snakes. Tony has endless recordings of him in battle, twisting and flipping and using that ornate spear of his to destroy anything that gets in his way.
Even when they aren't in battle Loki moves as though every step is choreographed, slithering around the mansion with the stealth of a thief or a spy. When he wants something he will approach Tony with a wicked little smile and a slight swing to his hips, and Tony will usually say yes before he's even asked.
Loki on his knees has to be one of Tony's favourite sights. The trickster kneels delicately, fluidly, and looks up at Tony through his long lashes as he unzips him.
Tony gets hurt sometimes in battle – it's just part of the job. Sometimes he gets hurt saving Loki. Loki is always very grateful, and Tony definitely appreciates it, especially when a cool tongue traces along the entire length of his cock.
“Christ.” Tony gasps, leaning back against the wall of his workshop, threading his fingers in the fine black silk of Loki's hair.
“You are reckless.” Is all Loki says on the matter of Tony getting hurt to save him, because it's only a few bruises down one arm and Loki would have come out of it a lot worse, magic or not.
“You love it.” Tony replies, voice slightly strangled because Loki takes him in and his mouth is cool and it's always strange but so fucking good.
“Mmh.” Loki purrs around him, perhaps agreeing.
Tony is surprised at what Loki will let him get away with in bed. There is nothing he has found yet that Loki will not let him do. He supposes it's because Loki has the power to simply vanish if he chooses to, but he never has yet.
Tony has been gentle – even torturous in it – and drawn one session of lovemaking out over hours until the sun is coming up and Loki is shaking and gasping and drenched in sweat on his sheets. He has been rough, left Loki with bruises standing out harsh and dark against his pale skin, teeth clenched against pain and pleasure and eyes filled with tears of both. He has tied Loki down, spread him, kissed every inch of that long, lithe body. He has pressed his tongue deep into Loki and relished the choked sounds he makes.
He has used toys that have left Loki wrecked and pleading for release, taken him in every position he knows and a few he found on the internet and painted his skin with sugary syrup so that he can lick it off again. There is nothing Loki will not let him do, and sometimes he almost wants to ask Loki why.
The things Loki can do in bed make him almost rethink his stance on hating magic. Loki shows him things he's never even though of, smiling in that seductive way he's perfected. He lets Tony suggest things and almost always finds a way to do them if it's within his power.
They've had sex on the ceiling, which was novel. The clones Loki can make of himself are one of Tony's favourite things – he's had two identical tricksters worshipping every inch of him before. He's also watched while Loki let one take him, the clone holding the true Loki down and knowing every pleasurable spot on his shaking body.
Loki can change his form any way Tony likes, and does so when Tony wants it. That is rarely, though, since there is nothing Tony can think of to add that could possibly improve upon perfection. He tells Loki this, smiling, and the trickster agrees with him.
Eyes truly are windows to the soul, Tony knows this. Loki's are filled with a dull pain that's present on some level even when he's laughing, and Tony knows it took years of not being loved quite as much as Thor to put that there.
His eyes are green – pale when he laughs, dark when he's threatening or upset and glowing slightly when he uses too much magic at once. Tony isn't surprised he's such a good liar when he has such large, innocent eyes. He tears up when something is truly painful to him, although it's usually emotional and hardly ever an actual wound.
When his magic flows through him Loki's pupils dilate. Tony zooms in on it from his suit when he has the opportunity and wonders if it feels good. His eyelids will flutter half closed while it flows out of him and he looks like he does when Tony is driving into him, though only for a moment. In battle he quickly drags himself out of it and one day Tony will ask him how it feels.
He's only seen Loki use up his reserves of magic completely once in all the time they've been together. Loki just lay on the ground and gasped for breath, unable to move, and his eyes were pinpricks of black in a sea of green.
Sometimes his eyes are red, glittering like rubies in a face sculpted from ice. Loki hates that form. Tony wishes he could change that.
There is a thin plait braided into Loki's dark hair sometimes, when he feels like a change. Tony likes it, even though Thor does the same thing occasionally and he doesn't really like being reminded of the thunder god by something that turns him on, because that's just awkward.
One of the most delicious states Tony gets to see Loki in is when he has just gotten out of the bath. He is usually wrapped in a large towel or perhaps the deep green robe Tony bought for him, gold trimming because he's a prince and he does the regal look better than Tony ever would. Tony does the covered in grease look well, though, and he knows just how much Loki approves of that.
Tony usually tries to catch Loki just after he's gotten out of the bath, while he's slightly flushed and his skin is still warm and damp. His hair hangs loose in an attractive mess, the little plait woven into it, and Tony always wants to fuck him then. Loki hardly ever lets him because he has just gotten clean, but he usually relents later.
Loki has nothing against kissing straight after a bath, though, and Tony enjoys the opportunity to bury his hand in loose, damp hair to hold the god of mischief's lips to his. He will always pull Loki's hair a little and Loki will always refuse to admit that it turns him on, even when Tony pulls his head back by it and kisses his throat and he gasps heavily. Now and then it will lead to more if Tony is very lucky, and afterwards Loki will drag him back to the bath and blame him for it all.
He really doesn't mind.
Loki is not a stable person. His grip on sanity is tentative, though Tony has calmed him down a lot according to Thor. He is usually fine when he is kept busy, but when boredom gnaws on him his mind starts to slip. Tony knows how it is to be smarter than everyone else and to need to have something to focus on.
When Loki starts to unravel Tony can see it coming. He's had a little practise by now and he knows how to deal with it, for which the rest of the team are eternally grateful. He takes Loki away for a couple of days if there's nothing to fight, and there usually isn't or Loki would snap out of it on his own.
They usually head to his Malibu home for a weekend and he lets Loki wander around the place for a while, strange and disconnected. When it gets late he takes the god of mischief to bed and Loki lays beneath him, quiet and subdued and just feels everything that Tony does to him. He breathes softly and his moans are hushed and Tony just makes him feel good, grounds him and brings him back. Sometimes it takes a few days but he always revels in the moment when Loki begins to respond to him again, just a brush of fingers through his hair or a smile or even just a few breathy words, something that's almost an apology.
“You are patient.”
And Tony smirks and says something nonchalant in reply - “For you, babe, anything,” - and is secretly terrified of the day when he can't bring Loki back. If he falls too far, if the unhinged laughter and the feral bursts of violence take him back Tony knows there'll only be one way to save him then. He'll do it, if he's forced to, because Loki made him promise he wouldn't let Thor. He always wonders if he could get back up afterwards or if he'd just take out his arc reactor and let his batteries run down. Loki seems to know the answer. Tony thinks that might be why he always drags himself back.
They both have nightmares. Everyone in the mansion has nightmares, even Thor, but when Tony wakes from dreams of shrapnel and fire a cool hand always slides onto his chest against the arc reactor, calming him.
He would call Loki an angel when he does that, only then he'd have to explain what an angel is and he doesn't think Loki would really get it.
Loki has nightmares too, every now and then. He never makes a sound with them, but Tony can tell when he's having one because he goes rigid, shaking in terror and breathing in harsh little gasps. They could be about any number of things done to Loki in the past that Tony has heard about, or any number of the things he's sure Loki has never told him. Either way he always shakes Loki's thin shoulders gently and wakes him out of it.
Loki never wants to talk about it, the same way Tony never wants to talk about his own nightmares. When Tony is the one trying to shake the lingering fear of it away he finds comfort in cool, soothing arms, long fingers kneading the muscles of his shoulders until he drifts back to sleep. When it's Loki whose eyes stare at the ceiling, haunted and pale, the warmth of Tony's touches chase the memories away and the trickster allows himself to sink back into sleep, the hum of the arc reactor reminding him he's in good hands.