Author's note/Disclaimer: A little crossovery speculation on who the Immortal actually was. All characters not owned by Joss Whedon in this fic are owned by DC Comics.
Edited slightly to accommodate a review or two, and to fix a minor mistake regarding the Immortal's age.
Also, for anyone wanting to know who Vandal Savage is:
X X X X X
The apartment door came flying in as though it had been made of toilet paper. And one of the cheap brands, at that.
Three colorfully-dressed men entered the room. The place was large and opulent -- though they wouldn't have expected anything less from an immortal like him. They took several steps inside the room.
Alan, Jay and Ted looked at each other. Ted was rubbing his knuckles. "The old heavyweight's still got it," he said.
"I know if I was a door I wouldn't want to go twelve rounds with you," Jay said.
Alan enhanced his voice and said, "Get out here."
A bearded man came out of what appeared to be a back bedroom.
Ted said, "Alright. Go put some clothes on and then get out here."
The man sighed. He supposed he should have known this was coming, even though this time he was fairly sure he'd had nothing to do with it.
"Darling?" he said. "We have company. Friends." He went back inside the bedroom
"Yours or mine?" came an improbably cheery female voice from inside the room. No wonder he was naked.
"Well, it's just that mine are also perfectly capable of kicking down doors."
"I suspect this one was punched, not kicked. And it was made of wood."
The woman's voice laughed. "Ah. Those friends. Give me a minute and I'll join you."
Alan said, "We really don't need to meet whoever your current conquest is."
Suddenly there was a wooden stake at his throat. "Funny," the woman said. "She's always wanted to meet you." She looked over at Ted and Jay. "No, really. I mean it. I mean, you guys have been doing this for what? Forever? Sixty years and still going strong. I've always been a big fan of your work. I've been doing something similar for only a bit over eight years and I'm already exhausted."
Jay swore to himself. They'd been so focused on whatever danger Savage might possess they hadn't considered that the woman might also be a danger. A rookie mistake. Their only excuse was that their recent battle against the current Icicle and his cohorts had been a long and tiring one, but it wasn't much of an excuse.
However: The woman's words and demeanor belied the stake. The years of experience that had failed them in anticipating the woman's attack now told him she wasn't going to do anything to hurt them.
Jay's instincts were proven right when she let Alan go, before Jay or Ted could do anything about it. On the off chance his instincts had been wrong, he would have had the stake out of the woman's hand before she had the chance to use it.
Alan turned around and saw the woman. She was short, and in her early '20s at most. "You have us at a disadvantage," he said.
"No, I had you at a disadvantage when I had that stake to your throat. If I remember correctly, that ring of yours can't protect you against wood. Fortunately, in my line of work, wood is kind of a necessity."
"And you are?"
"Oh. Buffy Summers. Vampire Slayer. On sabbatical at the moment. And you would be the Justice Society -- three of them, anyway. Green Lantern," she said to Alan Scott. "Flash," to Jay Garrick. "Wildcat," to Ted Grant. Nice to meet you."
"Vampire Slayer?" Ted said. "What's the kid talking about?" Alan had heard of the Slayer; he had a connection to magic the other two Society members didn't have. Still, they ran in such separate circles he suspected he'd never net one before now.
The immortal came back out of the bedroom, now fully clothed. "The 'kid' is talking about killing demons and vampires. She does it for a living. I believe even someone with your limited world experience has encountered a few of these creatures. And certainly, having worked with a powerful sorcerer such as Dr. Fate --"
"Okay, okay, I get it." Ted said. "You're a big steaming force of good. So why are you hooking up with a villain like him?"
She shrugged. "I seem to have a weakness for villains, reformed, semi-reformed and otherwise. And he's terrific in bed. I mean, think about it. A guy with fifty thousand years of life experience is going to pick up a few tricks along the way."
Alan looked at Jay. "Not something I needed to hear." Probably true, though.
"Still," Buffy said. "We had a deal, Van. No villainy while we're together. I'd hate to have to join up with these three and start pummeling you."
Now it was the immortal's turn to shrug. "I haven't done anything more evil than stiff a waiter in the last two months. Why would you think otherwise?"
"The newest Icicle and a couple of his friends had a plan they swore was devised by you," Jay said, and explained the details.
When he was done, the immortal laughed. "They're right: I did devise that plan. Back in the 1940's. Even back then I gave it up as completely unfeasible. The original Icicle must have taken it and passed it down to his successors. You say this was last week?"
"Thursday through Sunday," Alan said.
"Trust me," Buffy said. "He was busy most of the time. I'd tell you how, but," she draped herself over the immortal. "I'm fairly sure you don't want the details."
'And," he said,"Since right now there are no warrants on me out in the country of Italy -- and you have no proof -- I'd appreciate it if you would show yourselves out."
He turned on his heels and walked back into the bedroom.
Buffy said, "One of these days I'm going to have to make that trip to New York. I bet you guys have a whole truckload of interesting stories. We can swap! In the meantime, though --"
She walked back into the bedroom as well.
Ted looked at Jay and Alan. "So, should we beat him up and take him anyway?"
Alan shrugged. "Even if he's being somewhat good now, this is just temporary. This is Vandal Savage, after all. He's been doing things like this for tens of thousands of years. He'll be back to his old tricks eventually. We can wait."
"What about the door?" Jay asked as they walked out.
"That he can fix on his own," Alan said.