Chapter title from "Rhiannon" by Fleetwood Mac. Rated MA, smut warning.

The steep, dark ascent to the Astronomy Tower seemed to leave Rhiannon breathless; weeks with moving around the dungeons and defensive spell work being her only exercise had resulted in her lungs being out of shape. The added cold from the late night air likely didn't help. Snape made a note that their defense training would have to escalate to the next level; she needed stamina.

Snape reached the apex of their climb first and was disappointed to see the night sky overcast, with only a faint moon for light. He could not risk frequent trips this far from the dungeons, and he had hoped she could at least take some joy in viewing the stars. But Rhiannon didn't seem to mind. She walked as close to the edge as she could before the knee-high rail stopped her, lifting her face to the skies, seeming to drink in the cold wind. It was almost surreal— she seemed like a beautiful white and green bird with a golden crown, ready to take flight, and she remained that way for minutes, soaking in the energy of the heavens. Severus Snape had never quite seen anything like it.

He watched, mesmerized. It seemed foolish to think, but she was like an ethereal queen— the cold rush of wind swirling her dress and her golden hair as if they would lift her up and carry her to some throne in the sky. It excited and angered Snape at the same time. He longed to possess her and feel the energy that would no doubt electrify them both once they connected; he knew enough about sexual magic to know that a witch and wizard's experience together was largely predicated on their level of power, the sheer raw force that flowed within them. Their union would be magnificent—if he ever allowed it to come to pass. But he was also enraged at the continued realization that he could not control her. He could placate her, subdue her for moments at a time with various distractions, but he was ultimately just biding time against a wild storm. Much like his relationship with her father.

Severus recalled the early days of meeting the Dark Lord as a young teen, always being a wizard skilled and knowledgeable beyond his years, but still in awe at witnessing Voldemort's expert command of the forces of earth and sky. Everything came naturally to him, as easy as the flick of a wrist or the gleam of a smile— whole worlds turned upside down, wishes granted, lives shattered, wills bent, every object and element seemingly beholden to him. To a young man who had only known rejection and disappointment, being aligned with such a force seemed the only answer, until it wasn't. With greatness came great danger. As he watched Rhiannon fall out of her reverie and turn to him with a victorious smile, her arms opening to him, he couldn't help but feel an uneasiness take root.

No. It's up to you, Severus, to make sure she is truly great, and never terrible. Over the years his inner voice had become that of Albus Dumbledore, an annoying fact that would leave the elder wizard elated if he were to ever find out.

"Thank you, so much. I love it up here." Rhiannon's eyes were glistening with tears. She was still holding her arms out as a gesture for him to join her near the rail, and he hesitantly obeyed. He was surprised when she not only took his hands but pulled him into a full embrace, her hips swinging into his, her lips locking onto his mouth with a hunger he could only describe as primal.

Snape backed away immediately, careful to steady her as he did so, since they teetered dangerously close to the tower's edge. "No," he told her, his tone leaving no room for discussion. He even instinctively grasped his fingers around his wand, fearing the power he'd felt from her during their brief encounter.

"Severus, stop fighting this," Rhiannon replied. She moved near him again but he stiffened this time and blocked her advance with his hands.

"The Potion," he told her firmly. "It's the only way."

"But why?" Her eyes were flashing with anger and she began pacing furiously back and forth along the floor of the Astronomy Tower. "It's ridiculous Severus. You want me, I want you, it's just sex."

"Not. For. Me." Snape replied emphatically. "Sex is complicated. It is a delicate balance of power. A loss of control. Emotions that cloud judgment. We cannot afford at this point to lose our focus. You have no idea of the danger waiting out there and the terror about to be unleashed."

"And running to a potion and a spell every time we feel the urge doesn't make us lose focus? It's no different!"

Snape could tell she had come down from her previous high and was firmly back in her haughty, indignant state of normalcy. Her goddess-like sexuality made it easy to forget she had only just turned 19, but her frequent petulant attitude served as an irritating reminder.

"The spell is very different. It's temporary, and it truly is 'just sex,' as you like to put it."

"Not. For. Me," Rhiannon mocked. "And what about the feeling afterward? You say there is no emotion, but there is. It's depressing. Lonely, sad, pathetic. I understand the spell's purpose for temporary separations, or situations where it's the only choice, but it's not the only choice for us. You know it's not."

She had closed the gap between them, her beautiful eyes lifted to his pleadingly, her hands grasping his forearms as his stood stick straight, arms crossed tightly in front of him.

"Have you forgotten that you are an engaged woman?" Snape asked her tersely. "Or do such trivial promises not matter to the Dark Lord's daughter?"

She shrank back, a look of hurt clouding her face. He had struck a nerve, and he felt guilty. She was clearly struggling internally with how her own identity related to her father's, though they had never discussed it.

"I don't do it to hurt anyone," Rhiannon explained quietly. "I want you both. I need you both. I don't understand it. It's like you both complete something, inside of me. Surely you understand how different you are from each other. How could you fulfill the same parts of me as he does, and vice versa? I can't explain it." She raised both hands to wipe away her tears.

Severus thought she had done a rather fine job of explaining it, actually. It made logical sense, as much as it made him blanch with disgust. But the fact remained that a choice had to be made. Dumbledore seemed to make it for her earlier today, but Snape was not about to enter into a marriage bond with her without certainty that he was indeed her choice, even if Dumbledore demanded it. He knew the headmaster simply wanted the magical assurances of her allegiance, and if Black wasn't a felon on the run, the old man would be just as content to achieve that goal using him instead of Snape. They were all just pawns in Dumbledore and Voldemort's seemingly eternal game of chess. Why it was always Snape's destiny to be pitted against these repulsive Marauders when it came to a woman's affections was beyond him.

But it wasn't beyond him at all. Snape knew full well what it was. Women wanted someone to make them laugh, someone to twirl them around the dance floor, someone to buy them nice things and play house, someone to charm the room at parties and make them feel secure in their place in society. Even exceptional witches like Rhiannon and Lily were still women at the end of the day, and they had those needs. Snape could offer none of those things, so why was Rhiannon even torn in the first place? Lily hadn't been. Or had she, and he just ruined it with his foul behavior that one day went too far?

Severus shook his head and turned to descend the stairs, having had enough of the searing cold wind and this conversation. He had enough preposterous emotions to deal with in the present without resurrecting analysis of Lily's past feelings. She would always be there as the undercurrent running through his every motivation, of course; after all, she was the reason he had made his choice to defect from the Death Eaters and align with the Order. She was the reason he devoted himself to standing guard over her son, as disappointingly dense and arrogant and frustrating as he could be. Even his Patronus was aligned with hers, as his moments with her were his only happy memories. So she would always be there, but Snape knew he had to focus his present energies on the here and now. The here and now was Rhiannon Aspenfell, and the needs of the Order dictated that he find a way to avoid the mistakes he made when he previously shared the love of a woman with a Marauder. He would have to lower some of the walls.

"Rhiannon," he called to her from the top of the stairs, working to soften his tone. Her back was turned to him as she stared out onto the Black Lake and the rolling hills below. Her former exuberance was now replaced by a stoic sadness, and she hugged the dark green cloak tightly around her to protect from the cold.

Snape returned slowly to the rail, lifting the long, billowing fabric of his outer robe and wrapping her in the excess, his arm securing it by encircling her waist. He caught sight of her emerald earring in the moonlight, and he gently kissed the spot of skin just below it, feeling her melt backward into him almost instantly. The knowledge that Rhiannon desired him so intensely was overwhelming — she was no fellow professor looking for a one night stand at work, no Knockturn Alley whore playing a role — she truly wanted him. She had said he fulfilled a need for her, that he helped complete her. No woman in his life had ever expressed such a thing. It warmed him, but also filled him with the gravity of holding a heart in his hand and being charged with not allowing it to break. While fighting daily to keep them both alive. He felt he was right to be hesitant, but she was clearly wearing on his willpower.

Snape's mouth remained at her ear, their bodies pressed together as his robe shielded them from the wind. He knew she could feel how much he wanted her, and for once he didn't try to hide it, instead trailing a hand down her stomach to press her more firmly against him. She moaned and closed her eyes in response, her head against his chest.

"If we are to do this," he whispered, "I need you to understand. I am not an easy man, and I never will be. And I can plainly see you are not an easy woman. This will be tumultuous, and trying. There will be times when you despise me. But I promise to give you pleasure like you've never experienced before. I promise to protect you— to die protecting you if it comes to that. I promise to transfer my own power to you through our connection, and to treasure your power as it is transferred to me. I will wait for you to give your heart to me, but I need you to promise your trust in me to keep you safe, and promise that you are entering into this because you want me — all of me. Because that is what you will receive."

Rhiannon was breathing heavily and nodding, biting her lip. Her hand traveled to his hair, pushing his mouth back to her neck. He nibbled the skin with a soft bite and she sighed. "Yes, Severus. Yes to all of it. Just take me, please. I want to be yours."

Snape turned her around in his arms and cupped her face in his hand, his mouth meeting hers. Their previous kiss had taken him by such surprise that he hadn't even registered the sweetness of her mouth, the delicate prodding of her tongue, and how she expertly commanded his desire with just a simple act.

"You ARE mine," he responded. "And I will show you what that means. You may not like it. Being with a dark wizard is different, even if that dark wizard works for the Light."

"I will like it," she insisted breathlessly. "I need it." She was up on her toes, taking her turn at his neck, kissing, sucking. He could have sworn she was even breathing in his smell— she inhaled deeply between her kisses, like she was taking in a drug and couldn't get enough.

"We need to return to the dungeons," Snape reminded her, easing her wild, writhing frame off of him. His erection ached in protest, but they needed to keep their wits about them until they were safely within the dungeon confines.

Rhiannon nodded, smoothing her clothes. "I'm ready."

He smiled wryly. "You are? I hadn't noticed."

She blushed. "I mean ready to go. To do as you instructed."

Snape led her down the stairs. "So obedient now, are we? Perhaps we should squeeze in a defense lesson while you're not defying my every command."

Rhiannon smiled at his teasing. "As you wish, Professor."

Rhiannon could literally hear the blood pulsing in her veins as they winded downward from the Astronomy Tower, from the highest point at Hogwarts to the lowest. It had to be midnight by now, and there were no stirrings at all within the castle aside from some snoring portraits and a passing ghost.

"Baron, you will say nothing," Snape muttered warningly. The ghost saluted in Slytherin solidarity but Rhiannon turned and saw his curious, transparent eyes following them down the corridor.

She couldn't believe it. She had won; he had acquiesced. She was going to sleep with Severus Snape. Her head was spinning.

When they finally entered Snape's quarters, they divested themselves immediately of outer cloaks, Severus stalking to his bedroom quickly and opening the door with a flick of his wand. He indicated with his head for her to enter, his expression impatient.

The room was more austere than she had imagined. The snakes were there of course, entwined like vines in dark cherry wood throughout his bed frame, coming together with married tongues at the apex of the canopy above. From the canopy draped black silk, currently pulled back to reveal a heavy, green brocade duvet atop silvery satin sheets that shimmered like scales in the lamplight. But aside from the bed, which was the very objectification of dark, magical sex, the rest of the room was nearly bare. A basic night table holding a lamp and a book, iron lanterns on the stone walls, and a simple, rather small wardrobe that no doubt held additional incarnations of his buttoned black suit.

Snape set his wand on the bedside table and ordered her to do the same. "No spells. This time." He sat on the bed and removed his heavy boots. She was positively shaking with anticipation, even more so when he stood and slowly walked toward her, almost menacingly. He grabbed her arms and turned her around, her back to him again as he grasped the sleeves of her dress and tugged them down. Once her shoulders were bare he sunk his teeth into her skin, and she screamed. It was only mildly painful— he had such perfect control— knowing the exact amount of pain to inject into the pleasure, as if he were measuring for a potion. His lips trailed up her bared neck, featherlike in comparison to the stinging bite on her shoulder. Rhiannon shivered and felt like one could drown in the pool of wetness that was forming between her legs.

As if on cue, Severus's hand pushed against the folds of her skirt, rubbing her back and forth through the fabric. She arched against his hand, desperate for more than just the tease of friction he was giving her.

"Such a hungry witch," he growled at her, his hand pausing. "I should make you wait."

Rhiannon shook her head with a whimper.

"Defying me again?" Snape whirled her around and threw her on the bed.

She shook her head. "No, anything you want. Please." It was like someone else had taken over her as she listened to her own words. Rhiannon nearly always dominated — she would let her partners have their fun of course, sometimes thinking they were in charge, but they always knew the power was hers and they willingly gave it. Even Sirius was content most of the time to lie back and let her take control— in fact he reveled in it. But with Severus she only needed enough control to get him to break down and agree— now that he had, Rhiannon was content to follow him wherever he would go. She had promised to trust him and she did. She couldn't imagine anything he would do to her ever being too much, so great was her ache to be filled by him.

"Undress me," he ordered.

Rhiannon sat up and eagerly started in on his buttons, but he caught her hand.

"Say yes first."

"Yes, my lord." Rhiannon smiled at his game and dove in for the buttons, each one like a little prize she won on her way to victory. Once the suit was removed, she started in on the white shirt's buttons, revealing his pale, strong torso, marked by a few black hairs and some scars. She knew each one had a story and probably ones he would never tell. Her mouth fell to his nipple and she sucked a bit before kissing down to her next task of his belt and trousers.

Severus shrugged off the shirt as she tugged on his belt, and Rhiannon caught a glimpse of his tattoo out of the corner of her eye. She stopped, suddenly pulled out of the moment.

"Does it frighten you?" he sneered. "Going to run away?"

She shook her head. "Never. I told you from the very beginning that I wouldn't run. I just—..."

"You just? What?"

"It's just...just so strong. So permanent. I don't really know how it makes me feel." Her fingers hovered over the Dark Mark, afraid to touch it.

Snape swallowed and looked at her darkly. She suddenly wanted to trace her fingers along every line of his face, caressing and kissing the stress and worry behind every curve, not to necessarily erase it but to appreciate it for what it was— every moment of his experience, his agony, his sacrifice. At some point she would. She wanted to spend the rest of her life loving and learning about this man, every one of his mysteries and layers.

Grasping his face in her hands, she straddled him and kissed his lips, falling back in line with her normal way of asserting control. For a moment it seemed as if he would let her. She was aware of his rock hard member pulsating against her, sending waves of heat through her as she felt herself opening for him even between their layers of clothes. Rhiannon was about to resume her work on removing his belt when he suddenly threw her off of him. She landed on the mattress, her head barely missing contact with the headboard.

"FUCK!" Severus shouted, grasping his left arm in pain. She watched in confusion as he scrambled for his clothes and boots, seeming to put on in seconds what it had taken her minutes to remove. He stalked to the door, his face even paler than normal.

"Your father is calling," he seethed, the door slamming shut behind him.

Rhiannon stared at the door in horror, feeling like she might cry. Instead she ran to the bathroom, vomiting violently. She grabbed her wand from the bedside table and quickly transfigured a toothbrush for herself to erase the foul taste.

Severus was right. She had no idea what terror lay before them. Dreams of dark magic were all fun and games when it came to plans for the bedroom, but this was the real deal. There was no telling what awaited Severus on the other side of this summons; there wasn't even a guarantee he would return. And the threat behind it all was her own flesh and blood. The thought chilled her, and she slipped beneath the duvet for warmth, leaving her dress in a heap on the floor. She inhaled Severus's intoxicating scent from the rich fabrics and closed her eyes, hoping to reach him through some kind of mental connection to see if he was okay.

That won't work, you idiot, she told herself. You haven't even united with him yet. It didn't work with Sirius even, and they had been together many times. A connection like that, like the ones she'd read about in magical romances, likely needed a marriage bond. It would be useful in situations like those Severus was forced to encounter, to have someone he could alert, although she was certain she would be forbidden from initiating the contact, to avoid the Dark Lord seeing her when invading his mind.

Rhiannon paused in her musings and was suddenly aware of the engagement band on her finger. Here she was entertaining the idea of marriage to Severus with a promise to Sirius on her finger. If he hadn't been summoned by the Dark Lord, she would have made love to him with that promise to another man on her finger. She knew she should take it off, until she reached a place where she was more certain. But she pictured Sirius's warm smile and radiant blue gray eyes— she imagined his tender touch on her cheek— and she couldn't bring herself to remove it. She wished for some way to talk to him, like she had with Severus. To try to make him understand. But she knew he would not respond as Severus had. Sirius was much too emotional, and already in a fragile state from Azkaban and still being trapped in a place he hated. Learning that she had almost slept with Severus Snape would break him.

So don't do it. Don't sleep with him. Leave his bed, now. He even tried to stop it in the first place. The only person who would be left disappointed is you.

Resolved to wait, Rhiannon gathered her dress and went back to her own room. Even if he returned safely, Severus's mind would be in agony, and it would be almost dawn. They would never recapture the heat and intensity of those last few moments before he was called away. His words raced through her head— low, passionate, and permanently implanted there now. He had promised to give her all of him. For a man like Severus Snape, that was no cavalier statement. And there was so much for him to give— so much he had likely never given to anyone. The prospect thrilled her, and she drifted to sleep focusing on that rather than the fear of what he may be facing while he was away.