Harry had been so close.

He was twenty one, it was his birthday tomorrow. If he could just survive the night...then even he died, he wouldn't become a siren. Tom wouldn't get the satisfaction of claiming him.

The creature circled him in the water, scarlet tail gleaming magnificent beyond measure in the late afternoon sunlight. Harry had remembered him being beautiful, his song lovely beyond all comprehension, and somehow reality managed to live up to the foggy memory of their first meeting.

But what did it matter if Tom was beautiful to more than a child's eyes? What did it matter that he hummed that seductive, wonderful, terrible song even now as he watched Harry tread water? Dunking him, holding him under, only to let him gasp for air again and looking at him like watching him nearly drown was the most exquisite thing he'd ever seen.

Harry didn't even have any of his weapons on him, to make it worse. The Death Eaters had stripped him of every last one, meticulously. So he struck out towards the shore, strokes strong and sure. It was a long swim, but he had to try, didn't he? He couldn't just tread water until his body failed him or Tom got bored and finished it.

"You know I will not allow you to reach land, don't you?" Tom smirked, flashing him those razor sharp teeth again. "You know you cannot possibly outswim someone like me in your current form. Though I do appreciate your efforts, your struggle to survive was one of the first qualities that drew me to you." The creature dove once more, and in a matter of moments his minutes of swimming had been dragged down to nothing. He was right back where he started, thrashing, as Tom released him to bob towards the surface.

This time, however, pale arms wrapped around him again.

Harry's jaw clenched as he seethed. He had three hours to kill the creature or he would become a siren too, and three hours where Tom would be most on guard to his attack.

But Tom didn't seem to be able to resist toying with him. Harry had found mer rarely could - the luring song was a game, but games didn't work with boys deaf to siren song, so they always got too close. Couldn't resist batting him around like a ball of yarn.

It had been the downfall of other mer, it would be the downfall of this one. He had to be clever about it though. Harry exhaled a breath to calm himself and twisted in the grip, settling his hand on the creature's shoulders.

"And how would you spend my last hours, then?" He studied Tom. "You've been waiting for thirteen years to make me yours, you've hunted me obsessively even when I cannot possibly be the only human you have marked. You must have made plans in that time."

"It's true, I have been rather busy since we last met," Tom said. "A mer does not become the ruler of the seven seas by chasing humans, however pretty the human." A sharp claw caressed his cheek.

Harry stilled. Ruler of the seven seas? But...no. "You said your name was Tom."

"It was, once upon a time. Nowadays I do tend to be known as Lord Voldemort, however."

Lord Voldemort. Harry sucked in a startled breath, fingers tightening on Tom's shoulders. It wasn't possible...was it? And was Tom boasting? He seemed like he was boasting, certainly looking for Harry to be impressed. He wasn't quite sure how he felt about that.

"I suppose I should be flattered that you came for me personally." Harry's mind raced through his options, heart pounding in his chest.

Tom flashed him another singularly lovely, singularly deadly, smile. "It is your birthday tomorrow, is it not, Harry?" the mer asked next, oh so slyly. "How could I not come for you personally on so a special an occasion? I think I like your timing, even if it was impudent of you to steal three years from me. There is a certain poetry to it."

"I wasn't aware your kind had much interest in poetry," Harry said.

"There is a lot you don't know about merfolk, Harry," Tom replied. "A lot your precious navy did not tell you. Let me give you a little birthday gift. Humans are fond of receiving presents, are they not?"

"Is this the bit where you say forcing me to become a siren is a gift?"

"I am not forcing you to do anything. We made a deal, one which must be honoured."
Harry felt Tom's tail coil around him as the mer pulled back to examine him, seeming distinctly amused.

"I was eight!" Harry snapped before he could stop himself. He'd hardly been in a state to make lasting promises and conditions for the rest of his existence. Especially when it had been a take the deal or die sort of situation. "Under duress."

"Human notions," Tom dismissed. "You will come to lose those in time, and see the truth of what you are being given. You adore the ocean - even when most would flinch away, you would walk along the beach as a boy. I would see you doing it."

A shiver ran down Harry's spine.

"You currently live a half life at sea. You swim with your legs, you move on your ships always distanced from the waters you love. You have no community among men because you were never meant for them. No family, not even as a boy. They tossed you to me and yet you would call me the monster for taking you in?" Tom's head tilted. "Humanity have poisoned your mind and I am your cure, Harry Potter. When we first met you looked at me like I was the most amazing creature you'd ever seen. What precisely is your objection to becoming one of us?

"I have no interest in luring people and killing them," Harry spat. "Maybe that's my objection."

"All creatures kill and hunt to survive. Do you condemn the fishes too for their natural instincts, or does it only bother you when the hunter and the prey has a face like yours? I know you eat fish."

Harry's stomach churned as he searched frantically for a good response for that, but, as the seconds ticked by with just the crash and spray of the waves, a wicked smile broadened across Tom's lips again.

"Humanity would use you," Tom said. "Turn you against those who would embrace you most. I do not hold what you have done against you, I am a generous lord you need not fear. You were misled. Amends will be made."

Even if he died, a human, and never became a siren it wouldn't fix this, would it? There would be other eight year olds desperate to survive, other humans sang sweetly to their death, other sailors who died because their captain had been chosen by the sea.

Harry steeled himself. This wasn't just about saving himself, about killing one creature however important…

"How are you going to turn me?" he asked.

Something flickered in Tom's eyes - Harry struggled to place it, some mixture between suspicion and triumph - and the mer reeled him in closer.

"Flesh, blood and bone. I'll make a little cut right here severing your fragile human skin…" he traced a delicate, teasing line along Harry's neck, right where the creature's gills would be.

Harry's breath hitched.

"Feed you a little of my blood...break your human legs...drown you…" Tom whispered the last one like it was the most intimate act in the world, leaning in as Harry's heartbeat even faster."And wake you up again with a kiss." They were so close that some part of Harry itched to lunge, to claw Tom's silver tongue out with his bare hands if he had to.

"Sounds like fun." Harry wet his lips. "What are you waiting for?"

Tom could have done that already, it seemed a simple enough process. He wouldn't even have had to risk untying him.

The mer pulled back with a surprisingly serious expression on his face. "Changing you is worth nothing if you do not complete the ritual once the transformation is complete. Your co-operation is helpful, as much as I am more than capable of ensuring you complete the ritual myself."

Harry swallowed, fingers flexing. "And what does completing the ritual involve?" He had a strange feeling that he wasn't going to like it.

"As you might imagine...flesh, blood and bone. Specifically, you luring and devouring your first human."

He was right. He didn't like it - at all. Could he really do what was necessary to take down the sirens completely? He'd always counted on the possibility of simply eating fish, instead of humans. Now...now he wasn't sure that was an option. To survive and not kill.

He supposed it explained why his mother had wasted away, instead of trying the same.

"Of course, there is also the fact that the ocean is a dangerous place," Tom said. "There's nowhere to hide, particularly, and the competition is more ferocious than anything you will see on land. Miles upon miles of open water...there is no room for civil war among my kind. There is little point in changing you if you are simply going to make my life needlessly difficult, I have a kingdom to rule and no intention of losing the throne.

Did Tom...know his plans? Certainly, he seemed to at least anticipate the possibility of a coup. Harry dared not look away as those pitiless eyes examined him. He raised a brow instead.

"So you were waiting for me to give my...consent?" It seemed a strange notion, from creatures whose mere voice obliterated willpower and ensnared humans entirely. It threw him off guard and Tom looked like he knew it, just like he knew Harry didn't expect sirens to have much appreciation for poetry.

"Do you?"

"What happens if I say no?"

"I'll drown you," Tom said. "Life or death, you agreed to be mine. As I said, deals must be honoured."

Harry considered his options, though it seemed pretty bloody obvious. Change. And then rebel later, civil war regardless.

It seemed simple enough, in theory. Except that still didn't account for the fact he had no desire to lure people and put them under his spell just by speaking. Not to mention the process sounded generally awful, and the thought of drinking siren blood made his stomach turn.

But what other choice was there? Die, and let some other eight year take the fall, let the system continue because he was too stubborn to do what was necessary?

No.

"Yes," Harry said, mouth abruptly dry. He never imagined he'd be saying that three hours ago.

Tom smiled at him and it wasn't remotely reassuring. Perhaps because for all the unholy glee on the creature's face, there still seemed something cold and ferocious to him. The something that made him fine with tricking terrified eight year olds into ancient contracts.

The water around them seemed to pick up, the faster churn of a storm that hadn't been brewing or anticipated a few seconds before.

"Relax then," Tom crooned again, trailing a claw up to guide his head back, exposing Harry's throat. "I'll look after you. Are you always so tense?"

"Only when I feel like I'm signing my soul away to morally dubious sea creatures," Harry said.

Tom laughed then, eyes gleaming. "The sea is a cruel mistress, Harry. It does not believe in human ideals of morality and fairness, how can you expect her children to be any different?"

"Just get it over with." Harry peered up at the sky, jaw clenched, the burnt orange of the setting sun dipping into glorious reds and bruised-purples on the horizon. The water lapped at him, as if eager to consume him too.

Tom's claw sliced in a heartbeat. Harry felt the emotion, but it took a second for the pain to hit. Then he gasped and choked, jerking in the water. His hand rose instinctively to clutch his throat and put pressure on the wound. Tom grabbed his hand, tail grip tightening on him in an instant holding him still and pliant as he shuddered. The mer's dark eyes seemed large and bright and hungry.

Maybe he'd made a horrible mistake. It was too late to go back, wasn't it?

The water around them tinged pink.

"Hush," Tom breathed against his ear, clutching him even closer against his chest. "Be still. I've always had you, hadn't I? I delivered you to salvation before."

A cool tongue dragged along the bloody cut on his neck, and Harry struggled to flinch away because he was pretty sure Tom hadn't mentioned anything about that! The mer hummed, an utterly pleased, self-satiated and seductive sort of sound in his ear. He had no idea if Tom was aware of it or not.

"You taste delectable," Tom said. "I think I would have chased you even if you weren't destined to be one of us. It's a pity really, that our kind always have the best flavour, though it makes you easy to find. Your first siren call."

Harry wanted to talk, but with a slit throat it was rather difficult. He settled for glaring as Tom met his eyes again, lips stained with Harry's life. This time, the smile he flashed was utterly predatory - no pretense at charm, just sharp teeth. His whole body felt as cold as if he'd been left in arctic waters.

Then Tom bit down on his wrist before shoved the offending appendage against Harry's mouth.

For a second, the wild urge not to drink bucked in Harry's chest again. A frantic sound escaped him. The second after that, the blood trickled down his throat. A small thread of warmth, a hook, the best ambrosia Harry had ever tasted in his life...and before he'd even thought about he suckled greedily. Eyes fluttering closed.

The world seemed distant, far-away, the Death Eaters and the events that led him there a dream.

It was over quickly, Tom tugging his hand free. "For someone objecting to murder," he teased. "You have quite the siren's appetite, Harry." The broken legs came without warning, before Harry had even finished blinking dazed and disorientated.

Tom's tail twisted.

The cry wrenched out of Harry's bloodied lips.

Tom dragged him beneath the waves, studying him intently as all surface sound faded away. Instead, Harry could hear the song louder now, that beautiful eerie song that had been haunting him since he was eight years old. It roared in his head, overwhelmed him as bubbles issued from his mouth.

He strained instinctively for the receding surface light, for air, as Tom dragged him down steadily into the darker depths of the ocean. His vision blurred. Black spots sparked in his vision. Everything hurt except for the small throbbing ball of heat inside him.

The blood spiralled and coiled upwards in the water from his neck - a scarlet hangman's noose.

Tom stayed close as Harry's life slipped away with each second that passed.

Hadn't he said something about a kiss? Tom was breathing. Tom had oxygen, of a sort, however stale and strange. Harry needed it.

He lunged forwards, only for Tom's fingers to curl in his hair.

Not yet.

Tom couldn't possibly have spoken aloud, but Harry heard it as clearly as if he had.

He could hold his breath no longer. The water flooded his mouth, sharp and cold in comparison to the heat of mer blood. His body spasmed again, jerked, only inhaling more dizzying water as Tom watched him eagerly.

His chest burned.

Tom trailed soothing fingers along his cheek and kept singing.

Harry's struggles began to lessen, body exhausted and bled out. His mind surrendered, settled calm. His eyes fluttered closed.

Lips ghosted against his own, before closing. Drawing him in impossibly closer, until Harry felt like he was in the coils of some monstrous sea serpent, until he felt they were fused.

The heat burst inside of him. The tingling sensation pulsed through him as their lips stayed pressed together. He moaned into Tom's mouth, tasting salt and copper. The spray of a wave, and Harry was falling, falling, falling into it…

It no longer hurt. If this was drowning, Harry could spend the rest of his life drowning in Tom's arms.

This time, Tom didn't stop him from reaching up a sluggish hand to his neck and the gills forming. Sharp claws shredded his clothes away - but Harry had no room for self-consciousness or embarrassment. Hands claimed every inch of him, the hungry mouth kissed him like a feast long denied.

He wasn't entirely aware of when Tom stopped kissing him, but suddenly there were teeth and lips at his shoulder, nipping and worrying at soft skin until it wasn't soft anymore.

Harry felt strong.

Fingers smoothed over his hips as skin turned to scale...gleaming, emerald scales and forest green scales and seaweed coloured scales.

The next thing Harry was conscious of was hunger. Ravenous, cavernous hunger as if nothing in the whole world could ever fully fill him up or satisfy. Hunger like fish hooks lodged into his chest, tugging him to hunt, to sing, to lure. Hunger like hunger was all that was left in him.

He scanned the ocean with clear eyes, tail twisting this way and that.

His gaze landed on Tom.

Go on, Harry. The siren' voice felt like a song in his head, impossibly richer and more nuanced than anything he could ever have comprehended as a human. Impress me.

Harry was off in a flash the song erupting out of him like vengeance.

When the fog in his head cleared Harry stared in horror at what he'd done. The shipwreck - the Dark Mark - lay in tatters around them. Bones picked clean and drifting towards the ocean floor, other creatures taking advantage of the carnage too great even for Harry's appetite.

The sea washed away the blood at his mouth, the murder on his hands.

Dozens of lives, and all because of his song, of his body a blur in the water that wreaked devastation.

Perfect. Tom again, a song of satisfaction and delight and wonder. I knew you would be, it's why I picked you. All that power. You are beautiful.

Harry shuddered, twisting his head this way and that as if he could shake the words and the voice right out of his ears. "I wasn't myself! I don't know what came over me - I couldn't think -"

It didn't come out as words, just bubbles beneath the water. He clutched at his mouth, his throat.

It's alright, you'll learn. The song isn't in your mouth it's in your soul. You will adapt quickly, I know it's overwhelming at first. I'll teach you everything you need to know.

"Where are you?" more bubbles. Harry couldn't see through the wreck, the husk of his enemies. At least it was Death Eaters and not a naval ship. Was that because they were closest or because some part of him had considered?

Harry wasn't sure he knew which was worse. Everything was the song - calling, calling, calling at him. A war drum in his head and he'd never expected that.

Tom appeared at his side, the only familiar thing and Harry thought he knew the ocean like home. The mer caught his hand, guiding him along until they were in clear water as well. He could see other sirens at the shipwreck now, feeding, harvesting, he had no idea.

I killed them. Did - was that all me?

He couldn't let this happen again. Screw his plans, screw taking sirens down from the inside, he'd beach himself. Surrender himself to the navy. Sing sailors to safety instead of doom, like his mother. How could he have done this?

It was your song.

Wasn't that the same thing? Tom said it like the song was something separate, beyond his control. Nobody had ever mentioned anything like that, ever. He stared at Tom, wide-eyed and shaken.

Come. Tom released his hand, grace embodied in the water as he spun and dove. I'll introduce you to your family.

Harry didn't know what else to do, so he followed.

A/N: So this is half repost of an old story I took off FFN, and half a new chapter. The reason for the repost is the new chapter seeing as this isn't just a random floating oneshot anymore, I hope you enjoy it and as always I'd love to get your feedback. The next chapter will be the last.