This story is a BtVS / Highlander crossover, a prelude to Bring Me the Head of Harry Potter, and is set about three years earlier, about eighteen months after Sunnydale fell. Harry Potter characters do not appear.
The religion mentioned below was invented by Tara Keezer for her story Stupid Portal (story ID 1333862), and is used here with her permission.
All characters belong to their respective creators / media companies / etc., this story may not be distributed on a profit-making basis.
Grounds for Divorce
by Marcus L. Rowland
"Okay," said Duncan MacLeod, "good parry, but you need to put more strength into a riposte and follow through while my guard is open. You're trying to kill me, not tire me out. Try it again from the start."
Dawn Summers backed off to a distance of fifteen feet then moved in again, dancing towards him with sinuous grace. She ducked backwards under his first swing, sliced at his ankles with the practice sword, then rolled clear as he tried to retaliate. The blunted edge of his sword grazed her arm, drawing a little blood. Sparks flowed up and down the wound, closing it instantly, as she swung for the coup-de-grace, but he blocked the strike and surged to his feet, knocking her back as she tried to overcome his strength.
"Much better, but what did you do wrong?"
Dawn rolled back again, spun to trip him, and rolled clear again. "Relied on crippling you with the ankle strike. You cheated, you should have stayed down."
"Right... Let's stop a moment." He got to his feet as she warily retreated. "That's potentially a good move against a normal opponent, might even put an immortal down for a few seconds, but you can't rely on it, it's too easy to miss the tendon. And you're wasting a lot of energy with these acrobatic moves, and giving me too many opportunities to retaliate. Someone with your musculature has to conserve her strength, win through superior skill. One perfect blow is worth a dozen near misses. Now, how about..." He stopped suddenly, feeling the buzz that warned of another immortal, and noticed Dawn moving towards the rack that held the real swords.
"I think it's okay," he said, recognising a nuance of the sensation - he wasn't surprised when the door opened and Methos came in.
"Duncan," said Methos, "and...?"
"Dawn, this is Adam Pierson. You can probably trust him with anything apart from your beer. Adam, Dawn Summers, my latest student."
"Delighted," said Adam, offering her his hand. "Would I be right to guess you're new to this?"
"A few weeks," said Dawn. "Someone shot me, in front of my sister and some friends. Fortunately I snap back pretty fast, they were still trying to resuscitate me when the sparks started. That was kinda tricky, everyone freaked out for a while, but once I'd convinced them I still had a pulse and a reflection we went looking for answers, and we knew a guy who knew a a guy who knew a lady who knew Duncan."
"And your sister wasn't upset?"
"She was pleased I was still alive. Well, alive again."
"Most people can't cope," said Methos.
"I guess it's a little weird," said Dawn, "but it's not like I'm the first person she'd seen that came back from the dead."
"She's in a peculiar line of work."
"You can tell him," said Duncan, "I'm pretty sure he knows about the things that go bump in the night."
"Okay... well, she's a Vampire Slayer."
Methos started, and in a long-forgotten language muttered "Sendaru, hunter of evil, destroyer of chaos!"
Dawn said "What?!"
"Nothing," Methos said hastily, "I've heard the stories, of course..."
"Bull," said Dawn. "If you know that name..."
"What name?" asked Duncan.
"Sendaru. Nobody knows about her any more, not since the Watcher's Council went down. I've come across it in some really old documents, I doubt anyone else remembers."
"He used to be a Watcher," said Duncan, a little confused.
"She's talking about the Watcher's Council," said Methos. "A very different organization. Though I'll admit that the confusion was occasionally entertaining."
"And you know the difference," said Dawn, "and you know that Slayers are avatars of Sendaru, the Slayer god. So who the hell are you?"
Methos looked at her, began to say something, hesitated, sighed, and finally said "Sister of Sendaru, I greet you. May chaos and evil pass you by."
"Holy crap!" said Dawn, "You're an initiate of Sendaru!"
"Not exactly," said Methos. Duncan suddenly realised that he was sweating and twisting his heel.
"Something higher then? A priest?"
"You're religious?" Duncan asked incredulously.
"You'd be religious too," Methos said angrily, "if there was a god around whose human avatar could snap your spine like a twig."
"So..." said Dawn, "Sendaru's sister is getting annoyed here. If you're not an initiate, and not a priest, what the hell are you?"
Methos sighed again, and eventually said "It was a long time ago, and I was young and stupid..."
"And I fell in love with the Slayer."
"Okay," said Dawn, "not seeing a problem here, it's not like you'd be the first guy to have a thing for a Slayer."
"I married her. To do that I had to join the cult and become an initiate, and sit through a lot of rituals I really didn't understand."
"How old was she?" Dawn asked coldly.
"Fourteen," said Methos. "Things were very different then. I thought I might be able to save her."
"How long did it last?"
"She made it to nineteen," said Methos, "went down fighting a demon army, it would be about where Berlin is today. They killed me too, but I came back. She didn't, of course."
"You did your best," said Dawn. "Slayers die young; it sounds like you kept her alive longer than most."
"That's not the problem," said Methos.
"So what is?" asked Duncan.
"I decided that it would be a bad idea to stay around, so I headed out towards Athens, wound up in Persia, and spent the next couple of centuries as a scholar around the Persian court. And then I ran into another Slayer. She took one look at me, and began to scream at me for running out on her."
"That's crazy," said Dawn, "I know Slayers sometimes remember their predecessors, but..."
"Predecessor?" said Methos. "It wasn't the Slayer that was screaming. It was Sendaru."
"I said I didn't understand the ritual."
"They married you to... to Sendaru?"
"That's about it," said Methos. "I barely got away that time, and since then I've run into Slayers half a dozen times. And every time Sendaru remembered me, and took over the girl, and I've had to run."
Dawn looked at him appraisingly, and said "Maybe you should try to get back together, settle things amicably."
"With your sister?"
"No, she's got a boyfriend, and I can't see Spike going for a threesome. But there are other options."
"I don't understand," said Methos.
Behind him the doors swung open, and a woman said "Dawn, are you gonna be much longer?"
Methos glanced over his shoulder, and three pairs of eyes widened and darkened. In unison Vi, Rona, and Shannon said "Husband?"
"I was trying to say," said Dawn, "that there are a lot more Slayers now." But she was talking to empty air. Methos was running, with three Slayers in hot pursuit.
"He's resourceful," Duncan said dubiously, as he heard doors slam and glass shatter in the distance, "he'll be okay."
"I guess," said Dawn, "and maybe Willow can try to talk Sendaru into giving him a divorce, if he'll hold still long enough to talk to her."
"Meanwhile," said Duncan, "it'll probably be a while before your friends get back." He drew the practice sword again, and began to circle around her. Dawn grinned, and settled down to business.