It's haunting how easily it settles in the back of his mind, purring with contentment and only interrupting him when it sees it necessary. It's worrying how easily he's able to ignore its presence, forget that his mind is inhabited by more than one mind (and how is that even possible is something he would like to know, because it sure as hell isn't DID, and science isn't really invested in demonic possession as it is).
But, more than anything, it should be much more alarming than it actually is how easily he accepts its presence, how reassuring it seems to be, unthreatening and helpful. He finds himself trusting it too quickly, comparing it to some sort of mental spirit animal of his own.
It's easy, because he knows it's voice since long before he heard it.
He's eight and walking through the forest in the middle of the night. His father is working, as always, and his mother is fast asleep, the pills that make the pain go away and make her sleep deeply taken hours ago. He thinks (dreams) he saw a light in the forest before, bright and beautiful, alluring, and he wants to bring it to his mother, because he remembers his body relaxing, eyes dropping heavily at the sight. He hates the pills his mother has to take, and thinks that the light is way prettier, and his mother would be much happier at having a beautiful light taking her pain away than having to swallow pills. So he's looking, hoping to see the light again, his oversized hoodie clinging to his pajamas as the flashlight in his hand points to trees and bushes, searching. Unthinking, he starts to go deeper into the woods, his teeth chewing the lower lip in a habit, uncaring that it will swollen and hurt in the morning. Eyes roam through the forest quickly, his step nearly a trotting, kinetic energy exuding from his pores. He gets distracted every minute, eyes widening at an odd looking tree or at an owl perched in a tree, watching him with lidded eyes. But he forces his mind to get back in track every time, the thought of his mother's smile enough to strength his determination and ground his mind for a while.
Long after the lights from his back, from civilization, have disappeared, his flashlight starts to flicker. He hits it with a hand, steadies the ray of light, and keep walking, until it finally dies, and doesn't turn on again. He frowns with his whole face, lips contorting into a pout as his eyebrows furrow and his eyes narrow slightly, nose wrinkling in a young gesture. The snap of a twig breaking makes his head turn instantly, distracting him from his annoyance, but the trees are shading the moon's light, so the only thing he can see are shadows and vague silhouettes. His eyes narrow, trying to drink into the little light, and he hears another snap, this one from another direction. Head snaps between the two directions, and dread starts to settle into his lungs, unforgiving. He hears (imagines, he tells himself much later) howls, and his heart seems to jump to his throat as the image of wolves, with sharp teeth and hungry bellies, fills his mind. He's running before he can think about it, the instincts to flee or fight kicking in as he hears the howls coming closer, louder. He runs and runs and runs, his body scraping and scratching with random branches. He trips over the root of a tree, and falls face first into the dirt, panting and coughing and rubbing the sleeve of the hoodie over his tongue because yeah, he literally bit the dust there. He's mulling over the foul taste of it when he hears another howl, and his body is tensing for another run, when a bright light shines over his face and he closes his eyes in pain for a moment, then opens them in surprise and looks amazed at the light he's been looking for for the past half hour, relaxing in its soothing arms.
(He thinks he hears someone asking him something, but he only remembers saying yes, and then everything is bliss and warmth.)
When he opens his eyes, he's outside the forest, and he flees to his house, not looking back at the silent, dark woods.
(He asks his mother the next day if there are a lot of wolves in Beacon Hills, but she assures him with a smile that there aren't wolves in California. He believes her.)
In retrospect, it's easy to see its traces, like faint footprints in the mud. Yet, as footprints that are disguised by the forest, it takes a certain level of knowledge to come to the conclusion that there's something aside from him living in his brain.
He can remember the little voice in the back of his head calling his attention when he got distracted, the way something inside of him seemed to tell him to look, observe the way other people moved, teaching him things that seemed totally logical and normal at the time. He can still see the books and books he'd been propelled to read by this same voice, his mind thinking nothing of what he now identifies as information of the supernatural hidden between folklore. At the time, he had thought nothing at picking up details he now realizes are truths.
(He remembers the librarian saying he was precocious and too smart for his own good at seeing his books on chemistry and human anatomy. He remembers the thrill that would sweep through his veins when he shot at his father's side in the range, the small whisper of bloodstained curiosity when he told him all he knew about guns, their history, how the new ones worked in contrast with the old ones. But, overall, he remembers studying how to make bombs and how to make someone die in quick, painful ways; thinking excitedly about the wounds the different bullets left, where he'd need to shot to make the most damage possible without killing outright. He always thought it was part of the darkness in his nature; he isn't so sure anymore.)
But if there's something he can't understand is why it backed down after his mom's death. Why didn't it take advantage when he was at his weakest, in the perfect place to manipulate him and even take possession of his body?
When he voices his question to the entity, the content answer he receives isn't satisfying at all.
"Because it would be no fun to take over you, boy."
And yet, isn't that against every trope about demons and possession and living inside someone's else head? At that, the demons laughs and squirms in the back of his mind, tickling him (and that's a weird sensation, to feel your mind being tickled) and managing to make him smile at the feeling despite himself. It's not the last time he thinks about it, but it's the last he asks, and the demon generally leaves him to his own thoughts.
The only times it interferes is when bouts of panic or paranoia threat to clog up his lungs, trigger a panic attack, and during these times all it does is envelop his mind, soothing like the light from all those years ago. It's nice and comforting, so maybe that's why he finds himself depending more of the demon's presence, keeping silent about the fact that there's another inhabitant in his brain to his pack of wayward wolves. He's not sure if it is commensalism or mutualism, but it doesn't seem to bother the demon too much, who does something that feels like a shrug in his mind and answers with a "Both". And yeah, like that makes any sense.
(It also gives him a vague answer when he asks if this thing they have going is some sort of supernatural version of endosymbiosis, which makes Stiles call bullshit and rename the demon "Deaton 2.0", and then "Deatwo". The demon laughs for hours at that, and he's never been more grateful that he can apparently turn on and off at will the weird "hear-a-voice-in-his-head" thing, Jesus).
With all the supernatural trouble outside his head, no one seems to realize him talking less, smiling more at random times and even breaking into poorly hidden snickers every once in a while. No one seems to realize either how he suddenly seems to know a lot more about supernatural creatures, and anyone who looks at him surprised immediately comes to the conclusion that he's been researching on the internet or memorizing the bestiary. All in all, no one asks him, so no one needs to hear the twitch in his heartbeat at the lie.
But, as everything goes in his live, nothing is bound to last forever, and it usually ends with lots of bloodshed and tears. In this case, it isn't so far from how it goes.
The hunters come without notice, and the first night they manage to nearly kill half of the pack.
As he presses the shreds that once was a shirt into Derek's wounds, driving with one hand and carrying in his Jeep five unconscious werewolves, part of his mind burns with fury and worry and need to protect, to maim those who hurt his pack, to kill. The desire burns fiercely under his skin, and he uses every ounce of control in him to not go after those bastards and fucking end them right then, the whimpers of pain and the burn of his own bruised ribs enough to remind him where he is. He can feel the demon squirming in the back of his mind, hissing with a fury that startles him for a moment. He knows it wants to end the threat as much as he does, but it stays quiet, giving him the space he needs to keep functioning, absently curling its tentacles of coldness around his nerves to make the pain of his broken ankle more bearable, healing the injuries that are hidden enough that no one will have reasons to suspect. It helps him stay grounded as he parks and limps into the vet to alert the man.
When their eyes met, Deaton sends him a glance that's just marginally too long, and then he's in the parking lot, helping the now barely conscious werewolves out of the car and into the clinic.
He doesn't say anything, so Stiles doesn't even try to use his time to worry about what Deaton might or might not know, too wrapped up in calling Allison for wolfsbane and using the medicine Deaton gives him on those who'd been shot with another type of poison to care.
The clock marks two o'clock in the morning when they're finally done and Deaton, Allison and him are covered in blood and other substances that definitely make the clothes unsalvageable. He's sitting, body aching and hurting in ways he's becoming familiar with as the years since the whole 'Scott getting bit by a radioactive (not really) wolf' pass, and Allison sends him a glare, coming with more bandages and orders that he follows silently, too exhausted and scared of her wrath to be witty or brush it off (and he can see she's pissed because they didn't call her, but come on, it was supposed to be a practice night and she'd just come back from a five day trip with his father from some hunter-related business!). It takes them another half hour, but when she finishes she nods with some sort of military satisfaction, and goes to burn the bloodied clothes and cloths, leaving him in his underwear, a clean set of clothes at his side. The others are in similar conditions, still healing the worst of it, but more dressed than him nonetheless. He ignores them, ignores the clothes, and just stares at the ceiling, breathing more easily as the painkillers start to kick in; he seems calm, but inside his head is a mess. He can hear the demon squirming, like chains clanking against the ground, and it's still hissing in barely contained rage. He wants to ask why is it so angry, why does it care, but only the thought of it makes the demon growl, its opinion at how idiotic those thoughts are clear. Stiles stops, mind blanking for a moment, and the sound of chains stop, along with the growling. Silence fills his head, and he takes a deep breath before expressing his suspicions in his mind. The demon barks a laugh before he finishes though, dangerous and self-depreciating, and Stiles finds himself blinking, thinking for a second that maybe it's DID. "You're not mentally ill, unless you consider your policy of ignoring everything you don't like until it disappears or turns unbearable as an illness." He doesn't, and the demon is well aware, seeming to relax in Stiles' unsaid answer. "Yes, I do care. No, I won't answer to question such as why or how. Kid, I'm a demon, not a fucking soulless creature." Stiles' snorts softly, a smile tugging at his lips for a second, and the demon seems to purr in response. "It's not my fault if you're all so idiotic and endearing." Stiles defends himself thinking that it's them who are the idiotic morons, he's by far the most thoughtful and leveled of all them, even if no one listens to him. Ever. The demon wriggles in what Stiles recognizes as an amused but conceding nod, and his mind turns silent once again.
He closes his eyes for a moment, and when he opens them he's in his room, lying in his bed with other four betas covering every inch of his mattress. He doesn't even wonder how in Earth did they all manage to fit in, seeing how he's being sandwiched between one very cuddly Scott and one even cuddlier Erica, and he can feel what has to be part of Isaac's body sprawled over his legs, and most likely also Erica's and Scott's. If the arm that' slightly poking his ribs is something to go, Boyd is most likely there too, half of him being used as Erica's own mattress and pillow. He blows at the stray strand of hair that's ticking his nose, looks up and yep, there's Derek, somehow looming even though he's sitting in the chair, looking at the bed with intensity. Even though his vision is hazy with sleep, he can feel the pair of eyes looking at him, and he groans, letting his head fall back to the pillow, which in turn makes Scott growl slightly and somehow paste himself against Stiles' side even more, his warm breath hitting his neck with a purr before he calms down again. He barely hides a snort, looking at Derek, who seems to be smirking, but looks like he has no intention of coming down there anytime soon. Stiles rolls his eyes, unimpressed.
"Stop sulking on my chair and come here, dude."at Derek's neutral face, he adds "I'm not letting you sleep on a chair, so come before I have to get up and bring you myself."
"There's no space." is Derek's calm, reasonable answer. And, if Derek is being the reasonable adult here? Then there's a problem.
(Not really, but Stiles is too tired to think clearly and look for something to really complain about, no matter how strangely adorable Derek's being acting like a papa wolf watching over his unruly and bedridden children.)
"And? If five guys managed to squeeze in a bed made for one person, then there' place for one more. I'm always open to the puppy fest." Derek growls at him, and both Erica and Scott growl back in their sleep. Stiles barely manages to contain the laughter, chest twitching in a way that isn't as painful as it should be, and he doesn't need to make bets to know they have used their pain leeching powers on him. Even so, Derek does come, slow and unsure, a little unwillingly (Stiles holds shut his mouth and avoids embarrassing him, as much as he wants to poke at his reluctance to get there instead of keeping watch over his litter), and makes place for himself at Isaac's side, still far away enough from the broken ankle. Silently thankful, Stiles listens to the sounds of breathing, his body relaxing in a way it hasn't since long before his mother's death, and he feels his mind softly vibrating with purring he doesn't know whose it is, until he falls asleep.
A week passes, and Allison tells them that, even though her father has tried to contact the hunters and make them back the fuck off, the outskirts of the town are still being watched. They obviously don't know who they are going against, or maybe they're just disrespecting Chris on purpose, but Allison's sneer is enough to convince everyone that the other hunters are not welcomed even by hunters. The demon whispers in his mind, the danger of leaving them to do as they wish taunting him, and he jokingly says that it wouldn't be their fault if those guys enraged something in the forest and got themselves killed.
Allison agrees, and it's all what he needs.
That night, the demon and him visit the hunters, and he lets it take possession of his body, the long conversations they've been having about it all week echoing in his mind.
It's disgusting how much the demon vibrates in enjoyment as the blood splashes against his skin and stains the old clothes. But it's much more disgusting how he finds enjoyment too, surrounded by viscera and dead bodies, predatory eyes fixed in the last, terrified hunter.
Both of them drink from his terror as he dies, and both whisper with a smile a last warning to the dying man's ears.
You shouldn't have hurt what's mine.
When the notice of the hunters' apparent death reach Chris and Allison's ears, he's long ago taken care of his clothes and his scent. The official (supernatural) version is death by a migrating Wendigo.
A smile slips from the depths of his mind, and Stiles feels the need to return it.
(It's the first of a long string of murders, but they manage to pull it off with various creative, diverse deaths. There's only one pattern: hurt the pack or the Sheriff, and they'll never be able to identify your corpse.)