A/N The Key thing had to come into it sooner or later, although things are different for this Dawn than her counterpart and none of them know that her power comes from the Key, they still have to deal with the fact that her counterpart's life was canon up until the fall of Sunnydale.
Johnathan6, I honestly did not think about the fact that Faith is The Slayer and The Slayer left their reality and the impact that might have on the Slayer line and now all kinds of ideas are brewing.
Xander meeting the Addams will be part of the follow-up stories series.
######
"Dawn, what did she tell you?" Xander asked, crouching in front of the girl he loved like a little sister.
"She wondered why I was so young. I didn't understand what she meant, I'm eleven, almost twelve. Of course I'm young. She told me the age they made her was fourteen."
"They who?" Xander asked gently.
"The Monks of Dagan. She said they guarded the Key, some kind of energy that could open dimensional gates. A Hell god called Glorificus came for it, to use it to get back to her home. She'd been exhiled after a war. They made her a fourteen years old girl and put the energy in her and sent her to Buffy, to protect. They made fake memories so everyone would think she'd always been there, but she hadn't."
"How did they find out?" Buffy asked, glancing at her mother and frowning. 'our memories are real, right?' she thought.
"Mom got sick, a brain tumor. Buffy thought Mom was attacked magically so she did a spell. A trance to see spells. She saw the other me...she didn't belong, she was forced in."
"A trance to see spells?" Diana murmured. "A pull back the curtain spell probably."
"Buffy didn't tell anyone at first, she didn't want to believe it and than she found a man being tortured. She managed to get him away from the woman torturing him, which turned out to be the Hell god. He told her they'd sent me to Buffy. That they'd made memories in everyone. The Hell god caught her and used her blood to open a portal. Buffy jumped in it to close it and died. Then Willow resurrected her and there was a whole lot of badness."
"Dawnie, listen to me." Xander took her hands in his. "You're real, I've done enough scans of all of us to know, you're real. Whatever our counterparts experienced, we're not experiencing it ourselves. Our memories of you are not fake, I would know. You know, I would know. How many realities have we been told 'Xander Harris Sees truth'? You are real, there is no lie in your existence. Is it possible the power you have was given to you, instead of you being born with it? Yes. No one else in this room was born with power, but most of us have powers, from a variety of sources. So yes, someone may have given you this power, but you were born a Summers. And if you were made instead of born, it wouldn't change how we feel about you. Did it change how our counterparts felt?"
'No." Dawn shook her head, tears sliding down her face. "No, they loved her, Buffy died protecting her."
"I don't understand how Buffy's death could close the portal." Joyce looked confused. "That doesn't make any sense, if Dawn's blood opened it how does Buffy dying close it?"
"The monk told Buffy they made my counterpart from her." Dawn answered, letting her mother hold her.
"What exactly did they say, Dawn?" Xander asked. "Word for word, if you can."
"My counterpart said, they made it human, molded it flesh from the Slayer and sent it to Buffy to protect. When my counterpart found out she freaked, thought she wasn't real. Wasn't a person, she hurt herself. Buffy got hurt protecting her and told her their blood was the same, Summers blood and put her bloody hand over where my counterpart hurt herself."
"And that's why Buffy could have an affect on the portal." Xander nodded. "She tied them together, blood to blood. Blood Magic is crude, but powerful."
"But why send her to Buffy in the first place?" Faith asked. "I mean, I was around as a Slayer too, right?"
"I guess you didn't get into that with your counterpart." Dawn mumbled. "She was in jail at the time, the whole being crazy for a while thing? It happened because she accidentally killed a guy that Buffy literally threw at her. Giles told Buffy it was an accident and it was, but he didn't tell Faith and she was going nuts, trying to pretend she didn't care and than Buffy and Angel kidnapped her and chained her to a wall and started saying things like she's like Angelus and she believed them and joined the Mayor and killed someone he told her to kill and there was a whole lot more badness and a coma and revenge and she allowed herself to go to jail to try to make up for it."
"We knew some of that." Cordelia told Faith. "We hadn't had a chance to tell you things we found out in other realities. Like Willow thinking she was getting power from a celestial and it was really a demon and twisting her and she did some bad things, some of which she thought was good things."
"Xander's counterpart mentioned other me getting lost in the darkness and working for the Mayor and wondering if it was Willow's fault. So I knew some of it too. The jail part, not to mention the coma and revenge, I hadn't heard about. If Willow wasn't responsible, was someone else or did I just go crazy?"
"There's too much coincidence for someone not to be responsible." Xander answered. "Giles was your Watcher, as well as Buffy's, but barely acknowledged you existed in the realities we've seen so far. He literally left you on the streets and that's not at all like the Giles we know. But the Willow who confessed said she was hoping to bring peace to the world through a Power that would be born through Cordelia and Buffy and Angel were brought together not so they could fall in love, but so they could bring forth Twilight. Willow was told Twilight would destroy all the demons and vampires and close the Hellmouths, which would help with world peace. It's possible that in multiple realities these various beings were working together to manipulate us and being different versions of each other, thought and planned alike."