They trained for three weeks before William found the portal.
It was not the same three weeks the house had spent training after Miralba, and everyone in it understood the difference without needing it said aloud — this time they were not recovering from a war already fought. They were building toward one they had chosen the terms of, as much as anyone chose the terms of anything against a demon queen with three hundred years of patience behind her.
KaSandra trained too, for the first time in longer than Thomas could remember training beside her rather than watching her already finished. The thread did not move the way ordinary magic moved, she explained, more than once, to a basement full of people trying to build formations around a power none of them had ever seen deployed at full strength — it did not respond to drilling the way Fenix's fire responded to drilling, or Niall's earth, or even Katherine's dark element, all of which could be practiced in small controlled doses until the body simply knew the shape of them. The thread answered to something closer to intention, and intention was harder to drill than muscle memory, and more than once KaSandra ended a training session sitting on the basement floor, exhausted in a way none of her physical training had ever exhausted her, having discovered some new edge of what she could do only by nearly losing control of it.
"You're going to hurt yourself learning this," Thomas told her, after one such session, the basement wall behind her scorched gold in a pattern that hadn't been there an hour before.
"Probably," KaSandra agreed. "I'd rather learn the edges of it here, in a basement, with people who love me close enough to pull me back if I go too far, than learn them for the first time standing in front of the demon queen with no room left to make the mistake safely."
He couldn't argue with that. He had built his entire philosophy of training around exactly that principle, and it cost him something to watch her apply it to a power he did not fully understand and could not, this time, help her drill the way he'd helped her drill everything else.
William found the portal's location on the nineteenth day, using a piece of the assassin's own rust-colored coat that Niall had preserved, against most people's initial objections, specifically for this purpose — a thread of connection strong enough, William said, to trace backward through whatever had sent her, if he was patient and careful and willing to accept that the tracing might take considerably longer than anyone wanted it to.
It took six more days. On the twenty-fifth, William called the house down to the basement with a look on his face that told everyone, before he said a word, that the waiting was finally over.
"It's not a place," he said. "Not exactly. It's a fold — the demon queen's realm doesn't sit inside this world the ordinary way, it sits adjacent to it, folded close enough that the right kind of door can reach through. I can build that door. I want everyone to understand, before I do, that I can build it once. If we go through and it doesn't go the way we need it to, I don't know that I can build a second one in time to matter."
The basement was quiet for a long moment.
"Then we make the first one count," Katherine said.
They suited up the following morning, in the specific quiet ritual the house had built over two years of doing exactly this — armor checked twice, weapons settled into the hands that knew them best, the particular silence of people who had done this enough times to understand that talking too much before a battle only gave the fear more room to grow. KaSandra dressed last, and differently than the others, in a version of the long dark coat that seemed, this morning, to hold more of the coven's gold-white light in its seams than it had ever held before.
"I need to say something before we go," she said, once the whole house had gathered in the kitchen for what William had warned them might be the last ordinary room any of them stood in for some time. "I know what I said, the last time this house suited up to fight the demon queen. I stayed behind. I told myself, then, that staying was the wiser choice — that a power I didn't fully trust was more dangerous deployed than withheld." She looked around the kitchen, at every face that had trained beside her for three weeks, watched her nearly lose control and pull herself back from it a dozen times over. "I'm not staying behind this time."
Nobody looked surprised. Thomas, watching her from across the kitchen, understood that the house had likely known this the moment she started training alongside them instead of merely instructing from the edges of it.
"I'm coming with you," KaSandra said. "All the way through, whatever's on the other side of that fold. I have spent years being the person who stands at the edge of this house's battles, protecting it from a distance because I believed my power was safer contained than unleashed. I don't believe that anymore. I think the thread chose this exact moment for a reason, and I think the reason is standing in this kitchen, about to walk into the worst fight any of us has ever faced, and I refuse to let it walk in without me."
Tierney reached over and took her hand.
"Good," she said, simply. "Because I don't think any of us were going to let you talk yourself out of it a second time."
William opened the door an hour later, in the same garden where a proposal and an assassin had both, weeks ago, changed the shape of everything that came after — the air folding back on itself the way it had folded in the kitchen the night of the poison, except larger this time, wider, a doorway built to carry an entire house through it rather than one dying man.
On the other side was not the garden anymore.
They stood in a meadow of dead flowers stretching toward a horizon that had no proper edge to it, gray sky pressing low and close over stalks that had once, KaSandra understood distantly, been something living and had been dead for longer than the meadow itself seemed willing to admit. In the far distance, past miles of that grey dead field, a castle rose black and enormous against a sky that held no sun anywhere in it, its towers reaching up into cloud the way a hand reaches up out of water, grasping at something the water had no intention of giving back.
"That's it," Niall said, quietly, his hand still flat against ground that felt, here, nothing like the earth he knew how to read. "That's where she is."
KaSandra looked at the castle, and at the dead flowers stretching endlessly toward it, and felt the thread stir inside her — not violent, not yet, but present, watching, the way it had watched every threshold she'd crossed since the mountain finally taught her what she was.
"Then we walk," she said, "until we reach her."