Title: Of Keys, Slayers, and Cruel Intentions

Author: Gabby

Summary: Instead of the monks making Dawn the key, Kathryn Merteuil is created to be Buffy's twin sister. And what happens when the handsome Sebastian Valmont is thrown into the mix? Spoilers for seasons 1-5 and Cruel Intentions.

Rating: R

Disclaimer: Not mine. All Buffy is owned by Joss Whedon. And Cruel Intentions is owned by…some other brilliant person who's name I don't know off the top of my head.

Author's Note: My first Cruel Intentions story, but definitely not first Buffy, first crossover, or first fanfic! I'll update as often as possible, if I don't it's because school or something interferes, I have the whole plot and story line down… it's just typing it and getting it posted. Feel free to leave comments and constructive criticism, but please no flames. Enjoy!

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"Sebastian!" Kathryn's shriek echoed through the house.

Sebastian came running into the room that Buffy and Kathryn shared. "What?" he gasped.

"Where the fuck is my necklace?!"

Sebastian paled slightly, but caught himself. "Maybe it fell off when you were out?"

Kathryn snorted, "Me?"

Sebastian rolled his eyes at his coke addicted sister, "Don't worry, sis. I'm sure your stash will show up eventually. Or we could stake your little friend Spike and you could snort his ashes."

Kathryn bared her teeth, "Dick."

"One which you won't be seeing anytime soon."

Kathryn snarled and threw a Jimmy Choo stiletto at his head. He quickly ducked it and slammed the door behind him, calling back "Bitch!"

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"Buffy!" Sebastian called, walking into the kitchen.

He found her sitting on one of the stools by the counter. Her eyes were puffy and her cheeks were tear streaked. She looked at him, then quickly turned away and wiped her cheeks with the back of her hand.

"Buffy," he said, walking over to her and putting a hand on her shoulder, "Are you okay?"

"I don't really wanna talk about it right now," she stated, staring into space.

"Okay, but I've got something to take it off your mind."

Buffy perked up a little bit, "What's that?"

"Kathryn is freaking out about her necklace."

Buffy groaned, "Do you think she'd notice if I bought her a new one that looked just like it?"

Sebastian smirked, "Hell yes she would notice. It's special… "

"Special?"

"I'm going to let you in on a little secret, since you let us in on one. Our lovely bitch of a sister is a coke addict."

Buffy cocked her head to the side, "That explains a lot."

Sebastian laughed, "Come help me find it?"

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"And they sent me to a doctor because they thought I was crazy, writing about vampires and demons in my diary. They sent me to a clinic, I was there for weeks. They stuck me with needles so many times and did so many tests that I finally just stopped writing about it, acted like it never happened. That appeased them. But you think they'd question all the ripped and bloodied clothes right? Never, not once. Sunnydale gave me a chance to start over. Mom was obviously still oblivious, until the end of junior year."

"What happened then?" Sebastian asked, looking up at Buffy sitting on the tombstone from his position on the ground.

"My then boyfriend went all monster on us and I had to save the world. She wound up seeing me stake a vampire on our front porch and I couldn't exactly pretend that didn't happen."

"Boyfriend? Monster?"

"Ready for a sob story?"

Sebastian smiled a winning smile up at her, "You bet."

"Angel was his name. He was a vampire, but with a soul. He had fed on a young gypsy girl who was the favorite amongst their clan. They cursed him with a soul so he could feel remorse over every person he had ever tortured or killed. Which was a lot, considering he was called the Scourge of Europe. Eventually he wound up over here and in Sunnydale. We teamed up to fight all the big nasties and fell in love. Then my birthday came around and there was a big to do, but there was also some pretty bad shit going down involving Spike and his girlfriend, Drusilla. She had a demon called the Judge sent in for her birthday. Let's just say he was an ass. So Angel and I went to fight him, got captured, got away and wound up at his apartment. We both realized how close we'd come to dying and the time was right and we… "

"Made love?"

Buffy nodded, "I guess it happened during climax… or maybe after? I'll never know, I never asked. But Angel lost his soul."

"How?"

"According to the spell if he ever experienced a moment of perfect happiness he would lose his soul. A moment of perfect happiness defeats the point of the spell, which is to punish him. So then he turned back into the evil soulless vampire he once was: Angelus."

"Oh. So… how did this relate to your mom finding out?"

"Angelus wanted to bring a demon to wreak havoc on the earth and destroy it completely. Its name was Acathala. So we were fighting against him and basically every other vampire who knew about it. Hence the one showing up at my house. And my mom seeing."

"How'd she react?"

"She told me to get out and not to come back. I wound up in L.A. for the summer, living in an apartment and working as a waitress. Then I realized I couldn't run from everything and came back. She opened up to it then, realizing it was a part of me. And it's been so nice having her know… not having to hide… I just wish I could help her like she's helped me over the years," Buffy said tearing up.

"Are you okay?" Sebastian asked quickly, jumping off and brushing off his Brooks Brothers khaki pants. "Does this have to do with earlier?"

"It's my mom. She's sick. They… they think there's something in her brain. They need to do surgery. I just found out this afternoon."

"Buffy," Sebastian soothed and wrapped her in an embrace.

Buffy's body started shaking and was racked with sobs. She muttered unintelligibly into his coat. She pulled away from him, wiped her eyes and looked up at him, "Sorry. Didn't mean to break down."

Sebastian smiled at her, "It's alright. Everything will be alright Buffy, the surgery will go well and you can help her get through this. You're the strongest person I know, in more than one way."

Buffy smiled weakly at him and went to speak, but before she could say anything he put a finger up to her lips, silencing her. She looked at him quizzically as he leaned forward. He gently kissed her on the lips. When he pulled away she was still staring at him. Sebastian wasn't sure if that was the right thing to do until she grabbed him. Her kiss wasn't gentle. It was passionate and energetic and sent shivers down his spine. His tongue danced with hers as she ran her fingers through his hair. He hoisted her up and then pushed her up against the nearest mausoleum. He made sure her feet were on the ground and let her go. He started unbuttoning her jacket, but Buffy quickly pulled her mouth from his.

"Wait, what're we doing?" She panted.

"Um… I thought it was rather obvious," Sebastian replied, kissing her neck.

"But you're my brother and I'm emotionally bruised and I just got of a long relationship and I don't want to use you and… " Buffy babbled.

"Right now, I don't care."

He pressed his mouth against hers again and continued to unbutton her jacket. He cupped her breast as she bit his lip. He let his hand linger a little longer and then pulled it away, "We should get home. Give Kathryn her necklace."

"Mhm," Buffy nodded and quickly buttoned up her jacket.

Sebastian grabbed her hand and they left the cemetery together.

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"What the hell?" Gunn said as he watched Buffy and Sebastian leave the graveyard.

"She's with him? This is gonna make my job a hell of a lot harder. I guess if worse comes to worse I could always call for back up. Angel would be ready and willing."

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"Here's your necklace," Sebastian said, throwing the coke filled cross onto Kathryn's cot.

She smiled slyly at him, "Fuck her yet?"

"Very funny, but no."

Kathryn pulled on a black Marc Jacobs boot and looked at him, "Too bad."

"Where the hell are you going?"

"Out."

Sebastian shrugged and watched her prance down the stairs.

"Well that's good I guess," Sebastian said to himself, "That way she won't hear anything about Buffy and I. Yet."

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"So, you're a vampire," Kathryn said, raising a perfect eyebrow at Spike.

"You bet, love," Spike said, watching her atop of the sarcophagus.

She was wearing a short flouncy black dress and sexy stiletto boots. She had her hair up and Spike just wanted to take it down and run his fingers through it. He tossed back another shot of whiskey and slammed the glass down. If he couldn't have Buffy he could have the next best thing. And she was pretty fucking hot, so it wasn't that hard to get very aroused. He walked over to her and pulled the clip from her hair.

"Hey," she snapped, "What are you doing?"

"Shut up," he snarled, smelling her neck.

Kathryn smiled to herself. She hadn't even been here for two weeks and she already had someone dying to sleep with her. The fact that he was ripped and British also turned Kathryn on, so this would probably be rather enjoyable.

"Do you always have sex on top of your coffin?" Kathryn smirked.

"Like hell I do."

Spike lifted her up and carried her downstairs. He delicately set her on the bed. She leisurely leaned on her side and propped her head up with her hand. Spike leaned against the wall and looked at her hungrily. Kathryn sat up and slowly unzipped her boots, revealing her toned calves, and threw them on the floor. She leaned back against his red satin pillow and covered a fake yawn with her newly manicured hand.

"Tired," she stated, closing her eyes.

"Tired, eh?" Spike asked, crawling up on the bed toward her.

He placed his hands on other side of her head and leaned down. He kissed her viciously and quickly pulled away, "How about now?"

Kathryn wrapped her arms around his back and pulled him down on top of her. His tongue quickly found hers and they were engaged in an intense make out session. Suddenly she pushed him away. He glanced at her, questioning. "Let's cut the chicken shit," Kathryn smiled and she unzipped his pants.

Spike laughed and pulled the flimsy, little black dress over her head, revealing sexy La Perla undergarments. He groaned slightly and she pushed him over on his back. She quickly stripped him of his shirt and pants, revealing… nothing. Kathryn smiled and unhooked her bra. She giggled slightly when she saw how much that excited him.

"Ready for the night of your life?" She purred.

"I've been around for a longtime, pet. You have a lot of things to compete against."

"Oh, I'll win."

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Gunn saw what looked like the Slayer walking into a crypt with a bleach blonde vampire. She looked like Buffy, but her hair was brown and she was dressed in a way he wouldn't expect the feisty blonde to dress. He shook his head; he needed to figure out what the hell was going on.

"This town is fucked up," he sighed. "And that's saying something for someone who comes from L.A."

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Author's Note: Hey guys!!! Sorry it's taken so long for me to start writing again! So many crazy things have been going on. But I'm gonna stick with this story and finish it, so please bear with me! Thank you so much for all the feedback and comments! Hope you enjoyed it! Get ready for the next chapter!