Author's Notes: Written for nearlyconscious on LiveJournal, who requested "Any pairing, and waterbondage".
Warnings: Incest, obviously. Bondage, nipple and clitoris clamps, object insertion, breathplay.
Bellatrix had promised Narcissa that if she behaved properly at the Christmas party, she would get a treat.
Narcissa had been sceptical – she hated parties and hated that she was supposed to be the sweet, girlish daughter who enjoyed them, but Bellatrix had whispered in her ear that the reward would be worth it, and Narcissa trusted her oldest sister.
The party seemed to go on forever – an endless parade of people for Narcissa to talk to and dance with and pretend that she cared about – and it came as a glorious relief when Bellatrix sidled up behind her and whispered in her ear, "Come with me."
A flush of excitement rose immediately in Narcissa's cheeks.
"Pardon me, Lucius," she told him, then followed Bellatrix out of the ballroom. She was already wet between her legs, picturing the wonderful, dirty things that Bellatrix might do to her.
Bellatrix led her into the lavatory, then turned to her with a wild, almost predatory smile.
"Are you excited, Cissy?" she breathed. She leaned down and turned on the water in the bathtub – so that no one would hear them, Narcissa presumed.
She nodded and shifted in place, rubbing her thighs together. "Ever so excited, Bella…"
Bellatrix purred softly, peeling Narcissa's white lace dress and knickers off of her. Narcissa shivered a little, more from anticipation than from the cold.
"You're so pretty, Cissy…" Bellatrix whispered. She reached around behind Narcissa and unhooked her bra, then groaned, taking her small, firm breasts in her hands and squeezing them.
"Hang on…" she whispered. Narcissa didn't want to hang on, didn't want to wait for even a moment longer, but Bellatrix reached into her pocket and drew out three pieces of delicate silver chain. On one end of each piece was a small silver clamp, and the other ends were hooked together in the middle. It almost looked like some sort of jewellery. Narcissa's face flushed and she groaned. Bellatrix leaned forward and carefully fixed two of the clamps to Narcissa's swollen nipples. The last arm of the chain hung down between her legs and she knew what Bellatrix was going to do with it even before she put her hand between her thighs.
"Oh, Bella, please–" Narcissa gasped, then she let out a pained groan as she felt the clamp pinch down on her clit. Narcissa felt so deliciously vulnerable, with these pieces of metal fixed to the three most sensitive spots on her body…
Bellatrix smirked and spun Narcissa around. She picked up her wand and a rope shot from the tip and twisted around Narcissa's wrists, binding them in place behind her back. The position forced Narcissa to draw her shoulders back, and the clamps on her nipples and clit strained a little.
"Ooh- Bella–" she panted, and then, "Mmm!" when Bellatrix shoved a washcloth into her mouth, gagging her.
"Don't talk, slut," Bellatrix breathed. She turned off the water and pointed at the bathtub. "Kneel down in there, Cissy, and do it now!"
Narcissa whimpered softly. She was aching between her legs and wanted her sister now. But she stepped into the bathtub and got on her knees, then looked at Bellatrix.
She was stripping – slowly, seductively, shimmying out of her clingy crimson dress, and Narcissa moaned through her gag. Bellatrix purred, clearly appreciating her sister's moans, then pulled the cups of her bra down to expose her breasts.
Narcissa felt a fresh twinge between her thighs as she stared at them openly. Bellatrix's breasts were large and plump and the bra pushed them up and together, and stabbed through each dark, rosy nipple was a small bar.
"Bet you didn't know your sister had her tits pierced, did you, Cissy?" Bellatrix breathed, and Narcissa shook her head. She was so desperate and she tried to mentally beg Bellatrix to fuck her, fuck her hard, so hard!
Bellatrix bent over to pull something out of a cabinet, giving Narcissa a perfect view of her backside and the lips of her plump, glistening pussy, then straightened up. She held what looked like a bent piece of black plastic. It was rounded, two or three inches in diameter and curved in the middle, giving it the look of a distorted letter J or a very bent letter L. Narcissa stared at it for a moment before she realized what it was.
"Oh!" she managed through her gag, and Bellatrix giggled girlishly. She hoisted herself up onto the edge of the sink and slowly pushed one end inside herself.
Her juices flowed down over it and pooled between her thighs and Narcissa tried to rub her heel against her pussy while she watched her sister fucking herself. Bellatrix gave it a few strokes, then pushed one end of the toy deep inside herself. When she stood up, her muscles must have been clenching around it because it stayed in place, bobbing between her thighs like a huge, jet-black cock.
Narcissa could have come on the spot.
She moaned through the gag as Bellatrix sauntered around and knelt down in the bathtub behind her. Narcissa was aching and her body heaved – she had never been as desperate for anything as she was, right then, for Bellatrix to fuck her.
"Turn around," Bellatrix ordered and Narcissa turned away from her, grateful that there was a mirror she could look into to get at least a glimpse of her sister. She craned her neck so that she could see her breasts. Bellatrix was playing with one bar while she slowly stroked the toy with her other hand.
Bellatrix smirked and bit her lips. She pressed the tip of the toy against her little sister's slit and Narcissa immediately spread her legs a little and leaned forward to give her sister better access.
The toy slid deep into Narcissa's cunt and she arched her back with pleasure. Bellatrix pulled the cloth out of her mouth, but before she could make any noise indicating how good it felt, Bellatrix had grabbed her hair and forced her head underwater.
Narcissa automatically shrieked, and when she tried reflexively to draw breath, her lungs filled with water. She coughed and sputtered and her body writhed violently, but Bellatrix kept her head underwater and all that Narcissa was aware of was a terrible burning in her lungs and a pounding between her thighs.
When Bellatrix finally released her, she came up gasping and coughing. Bellatrix caught onto the chain attached to Narcissa's nipples and clit and pulled. The tug on the chain made Narcissa tighten around the toy buried in her pussy. She rocked back involuntarily against Bellatrix, who laughed breathlessly.
"That was hot, wasn't it?" Bellatrix whispered. She thrust her hips forward and Narcissa groaned. She threw her head back and looked up desperately at Bellatrix.
"Wh- what- was that?" she asked. Her voice was scratchy and rough.
"I like scaring you, Cissy," Bellatrix breathed. She tugged the chain again and Narcissa let out a small cry. It hurt badly, but she loved being in her sister's control…
She opened her mouth to say so, but before she could get the words out, Bellatrix plunged her underwater again. She writhed against her bindings, but with every passing second that she spent underwater, it felt better. She couldn't breathe and her head was hurting, her mind going hazy, and all she was aware of was the burning ache in her nipples and clit, the way her wrists strained against the rope, the unbelievable feeling of fullness inside her…
Bellatrix jerked her up by her hair and she managed one gasping lungful of air before her face was underwater again and Bellatrix was pounding her so hard that it almost hurt and she couldn't hold on much longer…
Bellatrix pulled her hair back again and Narcissa managed to gather just enough air to gasp out, "Oh, fuck!" and then she was over the edge.
She felt like she was coming apart, her lungs being torn apart by the water, and she loved it. She loved the pain. She loved the way her sister hurt her…
When she had finished, when her inner thighs were hot with come and she was finally able to draw breath again, she turned and looked at Bellatrix.
Bellatrix's face was flushed, and her whole body heaving.
"Oh, Cissy," she whispered. "You look so pretty when you're drowning."