It didn't take long after the kanima was beaten for Peter to lose interest in the proceedings. If he was being completely honest, he'd been tired of that whole melodrama before the night had begun.
"Well. This has been…eventful."
There was no response. Scott didn't so much as glance at him, nobody did except Stiles, but Peter was fairly certain Stiles just needed the excuse not to look at his first love embracing someone else. For a brief moment, Peter almost felt sorry for him, or at least sorry for the badge of pain stricken across his cheek. Then Stiles's eyes drifted, landing and lingering on Derek, and the feeling passed, as those things often did for him.
Peter didn't waste any time wondering why the emotion was fleeting. He wanted to leave, urgency and opportunity screaming in his blood, but he kept himself where he was. The moon was high in the sky, and he couldn't leave without Derek, his nephew who was still shaking off the betrayal he should've seen coming, would've seen coming if he'd been anything but foolishly trusting since the beginning. It was unbecoming of an alpha, truly, and Peter resolved himself to treating Scott like the threat he was, just as soon as he had the alpha power once again.
Eventually, Derek managed to pull himself together, and they left without another word to anyone there, not even to Derek's last beta. Something felt broken there as well, a perfect new addition to the already broken Hale family, and Peter was only grateful when Lahey turned to Scott instead of following mutely behind them. As weak as the loyalty was, Lahey treated Derek as his alpha for now, and if Lahey didn't follow, at least Peter wouldn't have to worry about subduing him as well. He knew he'd need all his strength for the alpha he had his eye on, and he wasn't going to waste his chance, possibly his only chance.
The walk back to the house was silent, and Peter bided his time, his hands opening and closing around the vial in his pocket. They had a while to go; they weren't there yet, not close enough for Peter's trap, and he cursed his instinct to spring now, while Derek was still weak from the kanima's venom.
After what felt like miles, Derek stepped over the first line of the trap and didn't react. Peter thought he hadn't noticed, except then Derek stopped, the lines of his back tense and outlined under the light of the moon.
"Are you going to try to kill me?" The question was frank, exhaustion weighing heavily on every word. He still hadn't turned around, but Peter knew that was only a façade of calm. The alpha power was there, barely under the surface, and after a night of betrayal and violence, Peter knew Derek was itching to draw more satisfying blood.
Answering was pointless and would've wasted precious seconds; Peter took his chance and sprang, claws and fangs already out.
To Derek's credit, the element of surprise was the only thing that gave Peter the edge. Even exhausted and wobbly on his feet, Derek's strikes were fast, well-aimed, although Peter couldn't help but notice they were defensive, only defensive. Peter's greater years of experience served him well, his own viciousness making him an opponent equal to a sluggish alpha. The fight drug on beyond the moment it should've taken between an alpha and a beta, and luck was on Peter's side. It wasn't more than a few minutes before they were tumbling to the forest floor, grappling for position despite blood and injury, and they stopped only when Peter managed to stretch a clawed hand around Derek's throat. Derek froze, visibly shaking from the effort needed to submit. Someone destined to be an alpha would never have been able to submit, no matter their strength, but this was Derek; unsuited to the position, from the very beginning.
Peter chuckled, mocking and cruel.
"My dear nephew. Still the beta, I see?"
"Shut. Up," Derek said through bared teeth, and in response, Peter tightened his hand around Derek's throat until his eyes widened and his pulse hammered against his palm. When Peter continued to hold his grip, Derek struggled instinctively, his arms twisting wildly beneath where Peter had them pinned with his knees. Peter watched with detachment until Derek began to slow, the lack of oxygen taking its toll, and then he reached over with his free hand, pushing against Derek's healing ribs until he couldn't hold back the choked whimper.
"You should be nicer to me," Peter murmured, loosening his grip on Derek's throat just enough to allow Derek to breath. "After all, I could slit your throat. Fair's fair, and all." He tapped his claws across the skin at the base of Derek's jaw, the heaving, vulnerable flesh that screamed to be pierced.
"I did what I had to do," Derek said, his voice resolute despite the thundering of his heart, and really, did the boy have no self-preservation? Peter almost admired that.
"True," Peter said, not angry, just resigned. His favorite nephew. The last of his family.
It was a shame, but necessary.
Peter sighed and leaned back to rest on his heels. When Derek swiped at him with an arm misshapen from poorly healing, Peter broke it again, easy like killing a rabbit. Derek never had learned how to channel his alpha strength when he needed it the most, and now he would never get the chance.
"You probably don't recognize this circle," Peter said, when Derek sank backwards, cradling his arm with anger in his red eyes. "It's from an older time. A better time, some might say."
"You talk too much," Derek said.
"You might be interested to hear this. It is, after all, a way to take the alpha power without killing you."
Derek stilled from where he was trying to shift away, to find space to heal, to escape.
"I'm not. All it requires is a little spell. A little blood, and I already have that." Peter waved his blood streaked fingers, catching Derek's eyes before he dragged them through the dirt around them, inside the circle. "Now all I need is your cooperation."
"Never," Derek spit, without pause. "You should never be alpha. You bit Scott, nearly killed a dozen teenagers, set the Argents upon us. Mom would hate what you've become."
The smile left Peter's face, leaving something darker, bleaker.
"You're right. My sister would hate me for all of this." He sighed again. "But, she'd hate me especially for what I'm going to do to her son."
Before Derek could react, Peter had launched himself forward again, moving fast with claws outstretched. Derek protected his throat, no doubt thinking that was Peter's goal, but it wasn't. Instead, he swiped his claws over Derek's heart, the scratches deep but not life threatening, and emptied the vial from his pocket into the cut.
Derek shouted, in pain and shock, and went limp like a broken doll. His eyes were the only thing still moving, and they watched Peter when he stood. The air stank of fear.
"It's not much. A little kanima venom from that mechanic's shop, a little wolfsbane from a distant forest. It won't kill you, and it won't last long. Just long enough."
Peter reached down and tucked his hands under Derek's arm, pulling his limp form into the exact center of the circle. Then he bent down and unlaced Derek's boots, hands gentle on his ankles as he tugged them off. He set them aside, outside the bounds of the circle, and then returned to remove the rest of Derek's clothes. He was gentle where he could be, careful of injuries already healing, but by the time he returned from placing them to rest next to his boots, Derek was whining high in his throat.
"I see you've figured out the meaning of this circle," Peter said, as he stripped his shirt from his chest. It stuck to the blood of a healing wound, one of Derek's lucky strikes—Peter owed him for that, something he would repay tenfold when he was alpha. "The spell was, obviously, meant to spare a husband or wife the pain of killing a sick spouse to become alpha. The result will be the same, either way." He kicked off his shoes, removed his pants and underwear. He set them with Derek's clothes, and then gave his cock an encouraging stroke. Despite the nauseating smell of fear and blood in the air, he had only to look over at Derek, prone and naked on the grass, to feel it begin to harden in his grasp.
He wondered, not for the first time, if he was as insane as people often claimed, but he pushed the thought aside. They were, of course, wrong, and it was hardly his fault if Derek was built well, nephew or no.
"I see why that boy stinks of lust around you, even while he claims to love someone else," Peter offered, a small comfort as he removed the bottle of lubricant from its hiding place behind a tree. Derek made a sound like a snarl, but it was weak from a near-paralyzed throat. Peter paid it no mind as he walked back to Derek, hand already extended to roll him over, a kindness so that Derek could pretend it wasn't him. Before his hands could touch skin, however, Derek gathered all his strength and spat at him. Peter froze, feeling anger rise up as he wiped the blood and saliva from his face.
He'd looked for days—weeks—for this spell, so he wouldn't have to kill his troublesome nephew. He'd planned it for when the threat of the kanima was over, for a time when being a family was once again within their grasp. Weeks before he made his move, and this was how Derek repaid him?
He pulled back, and Derek watched him. Peter's eyes trailed over his form, lingered on his defiant eyes and the vulnerable skin of his neck, his belly. An urge came over him, lust and anger, and he considered it.
"Why not?" Peter asked himself. He patted his side, the blood still tacky on his skin. "I do owe you for this, after all. And all the trouble you've caused."
Without another moment's hesitation, he crouched to the ground. He pressed his palms to Derek's thighs, spreading his legs as wide as they would go and then lingering on the soft skin. Derek was making noise again, perhaps the beginning of pleading words, but Peter ignored him as he bent Derek's knees, planted his feet in the grass, arranged him just so. It left Derek displayed like a sacrifice, his unresponsive cock resting against his thigh, the vee of his legs welcoming even though his expression was anything but. Peter reached over and lifted his mostly healed arms above his head to complete the sight.
"My, but you are beautiful, aren't you?" He trailed a hand down Derek's arm from wrist to shoulder, then across his chest until he encountered a nipple, which he gave a cruel twist before releasing. "You're lucky this hasn't happened before, frankly. It's really your fault, looking like you do. Like a masterpiece, begging to be destroyed, with power you never deserved." He tapped his claws against Derek's thighs, pressing hard and watching blood bead up even as the pockmarks healed. He wiped the blood off onto the ground, just to be certain the spell would take, and then reached once more for the lube he'd set aside.
Lubricant in hand, he scooted backwards and wasted no time in spreading the cheeks of Derek's ass to stare at pink skin. The pucker of his hole was clenched tight, as though it had been his last conscious movement before paralyzation struck, and Peter laughed, feeling his cock jerk in anticipation. He released his grip on the firm mounds of Derek's ass, then dipped one finger in the lube and rubbed it against that tiny opening, delicately feeling the warm, soft skin and prickly hair. He was absurdly pleased when there was an involuntary twitch in response, because while Peter was certain no one had ever had Derek like this, his body obviously didn't mind. He massaged him in small circles for a few moments, taking his time until the rim of his hole began to catch the tip of his finger and Derek's cock stirred slightly.
Well. Peter didn't want that, even if Derek would no doubt be ashamed of his response later.
He pulled back, dipping two fingers in the lube, and then shoved them inside him in one sudden movement. Derek choked on a scream, barely held back, and Peter smelled fresh blood as Derek's hole clenched, trying to expel the intrusion with heat and tight flesh. Blood was not a consequence Peter had expected, not for a werewolf body, but he doubted it could hurt the spell's chances, and with that thought, he began thrusting his fingers hard and fast, enjoying the way Derek's hole clung to the width of his knuckles.
Derek couldn't hold back every groan, and when Peter changed two fingers to three before his hole had barely loosened, he cried out like he was being torn apart. Peter smiled and shoved another finger in, just to hear the sound again.
He continued his thrusting for a few minutes, letting the sounds of pain and slick motion fill the night. There were tears on Derek's cheeks before long, glistening in the light of the full moon, and Peter felt himself harden impossibly further as he removed his fingers and saw them coated with lubricant and the barest traces of blood. He wiped them across Derek's lips, gentle, before thrusting them into his mouth, in and out, foreshadowing things to come.
Derek looked at him, then, with hatred in his eyes. Defiant to the end, and Peter loved it, suddenly wanted to come all over his insolent face, fill his pretty mouth. Perhaps later, once he was alpha.
Peter held his eyes as he lined himself up, and then thrust in slowly, making sure Derek felt every inch of hard cock in his virgin hole. The pleasure was indescribable, an almost brutally tight sheath around him, and it was made only better when Derek's eyes slowly closed in defeat. Peter continued to thrust his fingers into his slack mouth even as he rolled his hips slowly, feeling Derek's firm ass against his hips as Derek's sweet hole spasmed and clenched, tried to force him out. Peter pulled his fingers from Derek's mouth so that he could spread his cheeks wider, watch the way his cock disappeared into the defenseless flesh. Derek's ass was made for fucking, the perfect and sharp slaps of skin against skin only emphasizing that he belonged under a stronger wolf. A better wolf.
At the thought, Peter picked Derek's legs up and rested them over his shoulders. He used the new position to fold Derek in half as he speared him with his cock, rapid thrusts that shook dust from the ground, aided by werewolf strength.
After long minutes, the tight clench of Derek's hole eased, adjusting to Peter's thrusts. All but welcoming him. A fresh spring of tears appeared at the corner of Derek's closed eyes, and Peter knew he'd noticed as well.
"That's right," Peter said, on one particularly hard snap of his hips. He felt the world begin to swim around him, a dizzying feeling of power, control, anger as he neared his orgasm. He began to thrust harder as the world changed. "Not even you can fight your body. I'm going to come in your ass, and you're going to smell me—feel me—for days. Injuries inflicted by an alpha." He thrust even harder and felt his claws begin to grow, his hand breaking to form the paw of the alpha form. Derek had never achieved that form; he was pathetic, and Peter rubbed his new paw roughly over Derek's soft cock and balls, twisted and pulled the delicate flesh as his bones continued to rearrange.
Underneath the pain, he knew his form was soon going to be more animal than man, and he slowed slightly. If he was kind, he could come before he reached that point, leave Derek lying there, used and leaking from his gaping hole but relatively unbroken. Peter was not kind. Never had been, to tell the truth. He slowed further, letting the change build.
When his cock grew larger, that of a wolf the size of a bear, Derek begin to struggle, enough power back in his limbs to reach up, to try and twist Peter off by a grip on his quickly growing fur. Derek's eyes blazed blue rather than red, lit up the dark, and Peter thrust in as far as he could go, pinned him down. He came to the feel of Derek struggling under him, the flood of pleasure making him howl as his hands flexed and drew blood. He knotted Derek good and tight, feeling his tiny hole stretch and rip to accommodate a knot larger than his fist as Peter filled him with wave after wave of come. More blood, more tears, and Peter kept thrusting, working his knot in and out of the abused rim with sloppy sounds. Come and blood leaked out, coating the ground and making Derek's ass shine prettily in the moonlight. Derek had gone limp beneath him; fainted, almost certainly, and Peter howled again, unable to resist leaning down to kiss Derek with his changed mouth, licking inside with his long tongue. Derek twitched beneath him.
The alpha had no time to react before Derek's arm shot up, claws already extended, and ripped out his throat.