Summary
When SHIELD interrogator Sigyn is called in to read the blood memories of a captive invulnerable to usual methods of questioning, all it takes for the mercenary vampire to defect is the first taste of one trickster god's blood.
Loki wastes no time in subjugating the addicted revenant to his own agonised appetites, but when the battle for New York is lost and the Scepter's dark veil falls from both their eyes, how will they bear their lingering mutual fascination from opposite sides of a prison cell wall?

Warnings past torture, dubcon, mind control, sexual slavery

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I've made like Loki with the Tesseract and travelled back in time to beta my younger self's first shitty Marvel fic! I still get faves on it to this day, to my amazement – and do really appreciate those who commented on the original fic, but I feel the execution didn't live up to the premise, particularly in regard to info gaps about the Infinity Stones and Loki's time with Thanos revealed in later phases. So here's a kinky, twisted revamp with the rating cranked up to 11 for a more mature audience (me).

[Inspirations: Selene (Underworld) + Rogue (X-Men) + Harley Quinn = reimagining of Sigyn with powers based around a vessel (bowl) myth metaphor; Remshi's meditations on The Lash (By Blood We Live); the vampire lore of Vespertine, an original paranormal romance subversion I was writing on a dare at the time]

Part 1
'voice of a smaller god'

Loki sat slyly surveying the band of freaks assembled in the bizarre airship on which he was held hostage. His watchful gaze fell beside him to a sinuous woman clad in black, raven hair brushing her collarbone as she swayed with the worsening turbulence from an elbow slung languidly through a harness. He studied her closely for a few moments, until she turned her porcelain pale face to him.

'You're not mortal,' he remarked coolly. He wondered why the archer he now controlled had made no mention of her.

His insight was met with stony silence, her only response an upward quirk of one graceful brow. The other occupants said nothing, even as their attention converged on him.

'What are you?' Loki enquired openly, disarmed with intrigue.

The woman lifted her eyes to his; crystalline ringed in midnight. Then plump, rosy lips parted on a pair of razorsharp eyeteeth. 'Thirsty,' she spoke.

Her reply was met with terse intakes of breath from her colleagues, who tensed at her admission, clearly afraid of this thirst. She dropped her eyes, a slight smirk pulling at the corner of her mouth.

'For what?' Loki asked, needing to know of what the others were so wary.

'The blood of a god,' she purred indulgently, dragging a predatory stare up his chest. Loki felt a thrill of mingled danger and desire unexpectedly shoot through him.

'Alright, back off Sigyn.'

The Captain grasped her arm and tugged her away. Suddenly lightning flashed outside, sending a ripple of trepidation across Loki's face.

'What's the matter, scared of a little lightning?' Rogers challenged him.

'I'm not overly fond of what follows,' the Prince of Mischief grumbled.

She had to see him.

Heated voices carried down the corridor as Sigyn made her way to the containment unit, slowing her steps.

'- The world's filling up with people who can't be matched, they can't be controlled -'

'Like you controlled the cube?'

'- Your work with the Tesseract is what drew Loki to it, and his allies. It is the signal to all the realms that the earth is ready for a higher form of war.'

'You forced our hand. We had to come up with someth-'

'- Nuclear deterrent? 'Cause that always calms everything right down ...'

'Remind me again how you made your fortune, Stark?'

'- I'm sure if he still made weapons, Stark would be neck deep into-'

'Wait-wait hold on! How is this now about me?'

'I'm sorry, isn't everything?'

Sigyn slinked past the lab, unsurprised to hear that the roomful of gifted human egos rubbing up against each other had sparked into an argument over their war weapons already.

Loki's eyes snapped up as Sigyn approached the glass cage encasing him, his gaze appreciating the fluid grace of the vampire's movements. 'What have you come for, more questions?' he welcomed icily.

Sigyn gently folded her arms and breathed, 'Just … taking your measure.'

As her gaze wandered over his foreign form, her tongue traced her fangtips beneath her painted, bloodless lips. She was fasting for this, so she could gorge as much as her veins could take. The mortals didn't trust her discipline, and working only when sated alongside agents on SHIELD headquarters was a strict condition in her contract. But every rule had its exceptions. This one was tall, dark, and devilishly handsome.

The captive specimen sat with regal composure in heavy armour of malefic metal and black leather. His hollowed features were set in an elegant scowl, with a gleaming turquoise glare that glinted with the cunning of a coiled snake. Sigyn briefly wondered to herself from whence his well of malevolence flowed. At any rate, he would make a fine meal. Her finest.

The observation drew Loki's ire. She stood poised with feline calm, openly staring at him like a bug in a jar without any regard for his opinion. He rose to his feet, clasping his hands behind him. 'And what breed of creature are you?' he sneered as he drew menacingly close to the glass.

'Vampire,' she provided briskly, content to quell his curiosity.

'And you feed on … blood?'

'Mm.' She dipped her chin in a prim nod.

'Exquisite,' he appraised with eyes roving keenly over her.

Sigyn clenched her jaw and cursed the irony of having come to inspect him, and finding herself evaluated. She let amusement adorn the corners of her mouth. 'Likewise,' she returned.

He visibly preened. 'Is this then the final line of questioning, seduction?' he teased.

'Oh,' sighed Sigyn wistfully, tilting her head in mock sympathy, 'I'm afraid not darling.'

Loki's eyes narrowed. 'Then tell me,' he chastised, 'why do you concern yourself with the fate of these mortals?'

'I can't have you invading my hunting ground and enslaving my food supply. My kind are a touch possessive. You're stepping on a lot of toes here,' she warned.

The invader cocked his head in consideration, and leant closer. 'Join me and I'll provide you all the sustenance you desire,' he offered smoothly.

He may have need for a Queen once he had conquered the lesser realm, Loki deduced, and truthfully there were none so worthy on Midgard as this immortal.

Sigyn fought to suppress a shiver up her spine – at the tempting offer of blood, or the tone of his silken silver tongue, she wasn't sure. 'Ask me again if you win,' she countered, flicking a goading glance at the security camera bracketed above them and the spying eyes and ears on the other end. 'I'm not entirely selfless.'

His charming smile twisted at her evasive rejection with troubling volatility. 'Have you no ambition?' Loki drawled in disgusted tones. 'You would sooner stand with your cattle than assume your mantle above them. Pathetic,' he spat. 'You'll dream of the power I offer when you're kneeling with all the rest.'

Sigyn serenely shook her head. 'You're mistaken. Your power will be mine soon enough,' she assured him, noting the resulting drop in colour from his face.

'What do you mean?' he hissed, disturbed by a feeling of uncertainty for a second time in this mysterious creature's company.

Her lips sealed into a smirk. Then she turned, and left him to ponder his fate.

'Come back!' he snapped, hammering his fist on the glass.

Back in the now less-occupied lab, Banner brandished a syringe. 'Say, mind if I take a sample of your blood?'

Her kin had analysed themselves to pieces already, but Sigyn indulged his curiosity and offered the doctor her forearm. 'It's not my blood,' she sniffed dryly. The scientist had been one of the few to come near her, and his openness was a welcome break from the others' wary glances.

After a vial was filled the needle slid from her vein, the tiny wound closing instantly behind it.

'Thanks.'

Sigyn resumed her inspection of the Scepter, its cyan glow illuminating her scowling gaze as she scrutinised its strange construction. Stark and Banner buzzed behind her, exchanging a volley of technobabble as they crossed back and forth between an array of touchscreens while they worked on tracking the Tesseract's gamma signature. Thor had lingered behind after the others stormed out, listening along and verifying the scientists' burgeoning understanding of the alien technology with the lore of his home realm. Agent Romanoff, Sigyn wasn't exactly sure, but she was glancing at Bruce with targeted frequency.

Their discussion turned again to speculation of Loki's agenda when Stark addressed her abruptly.

'Your vampy voodoo picked up on anything so far?'

Sigyn bristled at his flippant manner, but considered the factors at hand. The spy had baited some information from their enemy already; he intended for the Hulk to destroy their airborne headquarters from the inside. As Captain Rogers had pointed out, Loki could not lead an army from the helicarrier. Among the secrets Sigyn was specially tasked with retrieving – the operation of the Scepter and the location of the Tesseract – she wondered how Loki planned to provoke the Hulk and escape unscathed.

'I'll know the answers soon enough,' she vowed.

'How many vials will you need?' queried Banner.

Sigyn flashed him a fanged smile. 'Oh no,' she clarified with relish, nearly shivering in excitement, 'I'm doing him old-school.'

And she wouldn't take no for an answer.

Tony threw Bruce an openly disturbed look, but the doctor's brow creased with concern. 'Are you certain a bite won't - you know - infect him?'

She shrugged a shoulder. 'He's Asgardian, I'm sure he's impervious to a trifling curse such as mine.'

'Curse?' said Thor, incredulous. 'On this world immortality is a curse? You've found yourself in the wrong realm, sister,' he chuckled. 'You should return to Asgard with me when this is over.'

The golden Prince's lack of prejudice charmed her. 'I'm not sure your people would approve of my appetite,' Sigyn pointed out.

She was not an Avenger, but a 'specialist consultant' as Coulson had put it; on-call for her talent for reading blood memories in captives less cooperative with interrogation by standard means. After three hundred years Sigyn had cultivated something of a predilection for sampling every haemic cocktail that appeared on her menu. Her work with SHIELD gave her access to some of the most powerful beings on the planet, and now she was privileged to taste the rarest of bloods: that of a Norse demigod.

Along with her prey's memories, for a time she would be imbued with their potency, harvesting whatever abilities or aptitudes they possessed. She would never be more powerful than with blood such as Loki's coursing through her veins. Her coven may frown upon her involvement in human matters but not even the elders knew the power of a god.

Her mouth watered in anticipation. By now the red howl in her marrow was almost deafening, a brutal bassline that reverberated through every parched capillary and throbbed along her jaw to each aching hollow tooth. It really took her back to the sixteen eighties. This was The Lash as she hadn't endured since she was a fledgling; primeval and intemperate.

She really shouldn't have looked at him.

At this rate, it was safest if she bunked down in torpor for the night. Sigyn retreated to retire to her suite when a smoky murmur breezed beside her shoulder. Natasha fell in step with her along the corridor.

'Everything okay Sigyn? You ah, seem a little ... tweaky.'

She was good. And braver than her comrades gave her credit for.

Sigyn muttered back under her breath. 'Why, Agent Romanoff, interested in an upgrade?' she invited.

'Thanks for the offer. I'll reconsider my DNR order.' The spy returned the flirtation and tailed her down a flight of stairs.

'You would be incredible, you know,' admitted Sigyn. 'With your skills -'

'I'm already pretty incredible. I can't see a debilitating addiction adding much to that.' Nat eyed Sigyn pointedly as she stopped outside her door.

She swiped her ID over the scanner and the bolts retracted with a hiss-click. 'Certain you want to be alone with me right now?'

'Better me than easier pickings.' Her olive gaze steeled on Sigyn with open suspicion. 'I've caught on to Coulson's misplaced trust before.'

She grimaced a beleaguered smile. 'Rest assured, our prisoner's is the only blood on this ship I want. I've been at this long enough not to spoil my dinner with junk food thankyou, nanny. I'm not the threat Loki has plans for.'

Nat rested a stubborn shoulder against the wall. 'You sure? Sounds like you two really hit it off.'

'Please. I was angling for a payrise. SHIELD salaries are barely keeping up with inflation.'

Sigyn pushed through the door, reaching immediately for the specially-installed thermostat. She keyed the dial below zero on an eight hour timer with tremoring fingers, before sinking onto the bed, one cold fingertip idly slipping between her lips to massage her burning gums.