They didn't talk for two floors.

  Kira moved through the trial corridors with the economical precision of someone who'd been doing this long enough to develop habits. She checked corners with her blade angled low. She paused at corridor folds to let the non-Euclidean geometry settle before committing to the passage. She kept Jack in her peripheral vision at all times: not watching him, but tracking him, the way you track a variable you haven't solved for yet.

  Jack let her lead. His body was running on fumes and borrowed time and whatever residual benefit the level-up had provided, which wasn't healing so much as a marginally improved tolerance for being damaged. His ribs ached with every breath. His forearm had swollen to the point where gripping the short sword required a conscious decision to override the pain signals his hand was sending. The lacerations on his back had scabbed and reopened and scabbed again so many times that the fabric of his shirt had bonded to the wounds in places.

  Kira glanced back at him once, early on. Her eyes went to the forearm, to the way he held the sword, to his gait. She didn't say anything. She didn't slow down either.

  Floor 6 was a corridor gauntlet. Narrow passage, low ceiling, constructs emerging from the walls at intervals, smaller models, fast and lightly armored, designed to overwhelm through numbers rather than individual threat. They came in pairs, then trios, then a sustained wave of five that filled the corridor from wall to wall.

  Kira fought the way water moves through a pipe: filling every available space, her blade cycling through the constructs' gaps with a speed that made the armor's reconfiguration irrelevant. She didn't need to wait for windows. She created them through volume. Six cuts in two seconds, each one finding a different seam, the cumulative damage cracking constructs open before their armor could compensate.

  Cleanup: Jack fought behind her. The constructs she damaged but didn't finish reached him with their cycling patterns already disrupted, their armor integrity compromised. He used Sever on the weakened boundaries: one precise cut where she'd needed six. Between them, nothing made it past the first ten feet of corridor.

  They were effective together. He could feel the rhythm forming: Kira's speed attacks disrupting armor integrity, his Sever strikes making the disruptions permanent. She broke things open. He made sure they stayed open. The combination was more efficient than either of them fighting alone, and by the third wave, their spacing had adjusted without discussion. She fought at the front with room to move laterally. He stood three paces behind, close enough to cover her blind spots, far enough to have reaction time.

  It wasn't trust. It was geometry.

  Floor 7 introduced environmental hazards.

  The combat chamber was larger than any Jack had seen, fifty feet across, irregular shape, the floor broken into platforms at staggered heights. The constructs were the standard shifting-armor model, three of them, and they weren't the problem.

  The problem was the floor.

  Sections of stone flickered between solid and boundary. Not crumbling. Phase-shifting. One moment a platform was real stone under his feet. The next, Edge Sense screamed a warning as the stone's physical boundary dissolved and the platform became a boundary plane: still visible, still present, but no longer solid. Stepping on a phase-shifted section was like stepping into the boundary lattice on Floor 2. The deep resonance. The disagreement. Except this time the disagreement was with gravity, and the result was a three-foot drop onto the tier below with nothing to cushion the landing.

  Kira found out the hard way. She was mid-lunge when the platform under her lead foot phase-shifted. Her leg went through what had been solid stone and she dropped to one knee, her momentum carrying her forward into an awkward roll that saved her from the construct's counterstrike but left her off-balance on the lower tier with her ankle twisted at an angle that made Jack wince.

  She got up. Tested the ankle. Kept fighting.

  Edge Sense showed him the boundaries of each platform, and more importantly, showed him the moment before the phase shift happened. The physical boundary of the stone thinned. Attenuated. Like a signal fading before it cut out. There was a window, maybe a full second, between the boundary thinning and the platform going non-solid.

  "The floor shifts," he said during a gap between construct waves. "I can see it coming. About a second before."

  Kira looked at him. Her ankle was swelling inside her boot. "How."

  "My perception skill."

  "Your perception skill sees the floor changing before it changes."

  "It sees the boundary between solid and not-solid. When the boundary thins, the shift is coming."

  She processed that. Filed it. "Call it," she said.

  He called it. They fought the remaining constructs with Jack acting as spotter: "Left platform, three seconds." "The tier you're on is stable." "Move now, that section is going." Kira adjusted her fighting style on the fly, incorporating his warnings into her lateral movement, using the phase-shifting as a tactical element rather than a hazard. She led a construct onto a section that Jack flagged as about to shift, then stepped off as the stone went non-solid. The construct dropped through the boundary plane and hit the lower tier at a bad angle, its armor cycling disrupted by the impact. She dropped down after it and finished it before it recovered.

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  Effective. Efficient. The rhythm between them was tightening into something that functioned like teamwork even though neither of them called it that.

  After the floor cleared, Kira sat on a stable platform and unlaced her boot to examine the ankle. Swollen but not broken. The chamber had gone quiet enough that Jack could smell it: stone grit and dried sweat, the faint mineral sharpness of construct dust settling on the platforms. She wrapped it with a strip of fabric torn from the construct she'd killed: the stone material was rigid enough to serve as a crude splint.

  "You fight wrong," she said while she worked.

  Jack was sitting on the tier below, his back against the platform edge, trying to breathe without making his ribs announce themselves. "Wrong how."

  "Your footwork is professional-grade close-quarters combat. Lateral pivots. Weight transitions. The way you step inside a swing instead of away from it: that's trained. Years of trained." She cinched the makeshift splint. Looked at him. "But your body can't execute it. You move like someone who knows exactly what to do and physically can't do it. Your muscle memory is ten years ahead of your conditioning."

  She'd been watching him more carefully than he'd realized.

  "Most people with your injuries and your body would fight defensively. Stay at range. Minimize engagement. You do the opposite. You close distance. You step into strikes. Every instinct you have is aggressive close-quarters and your body pays for it every single time." She paused. "That's not a class behavior. Classes don't give you ten years of muscle memory at Level 2. That's something else."

  Jack didn't say anything. The silence between them filled with the hum of the trial's ambient structure: that low vibration Edge Sense registered as the stone breathing.

  "My class gives me speed scaling and edge-weapon proficiency," Kira said. "Everything I do in a fight comes from Saber's skill set. My footwork is system-assisted. My reaction time is enhanced. I fight the way my class tells me to fight because I've had this class for..." She calculated. "Nine hours, and nine hours is all I have." She finished the splint. Tested the ankle. Stood. "You've had your class for less time than I've had mine. But you fight like a veteran. Not a Threshold veteran. A something else veteran. And you haven't told me what that something else is."

  "No," Jack agreed. "I haven't."

  She studied him. He met her gaze and let her look. She was smart, observant, and building a model of him that was getting closer to the truth with every floor they cleared together. She wouldn't get all the way there, regression wasn't something you guessed at, it was too far outside the frame of reference, but she'd get close enough to know that his story didn't add up.

  "The trial is converging us for a reason," Kira said. "Whatever's on the deeper floors requires cooperation. I need to know what you can do. Not just the perception skill and the boundary-cutting. The other thing. The thing that makes you fight like someone who's already done this."

  "I have experience that doesn't match my level," Jack said. It was the most truth he could give her without giving her everything. "I can't explain it in a way you'd believe right now. What I can tell you is that my instincts are reliable even when my body can't back them up. I know how to fight. I know how to read combat. And I know things about the system that I shouldn't know."

  "That's not an answer."

  "It's the answer I have."

  Kira's jaw tightened. She was a person who operated on clear information and he was offering her fog. But she was also a person who'd survived nine hours in a Tier 3 trial by being pragmatic, and pragmatism meant working with the assets available even when you didn't fully understand them.

  "Fine," she said. "Keep your secrets. But if your experience..." She gave the word a weight that said she'd be revisiting it. "...tells you something that affects my survival, you tell me. Immediately. Not after you've decided whether I need to know."

  "Agreed."

  "And stop fighting like you have a body that can take hits. You don't. I've been covering your openings for two floors and my ankle is compromised now. If you go down, I can't carry you."

  "I know."

  "Then fight like you know it."

  She turned and walked toward the exit corridor. Her gait was altered by the splinted ankle: still controlled, still precise, but with a visible compensation on the left side that she'd need several levels of passive regeneration to fully correct. She was adapting. She was always adapting. It was the thing he recognized most clearly about her, because he'd seen it in himself for ten years.

  Jack got to his feet. The movement cost him a currency he was running low on. There was copper in his mouth from somewhere, old blood he hadn't noticed until the talking stopped. His body was a ledger of debts: the hip, the ribs, the forearm, the back, the shoulder from the construct's elbow on Floor 3. Each one a line item drawing on reserves that weren't replenishing. In the first timeline, a Vanguard at Level 2 would have healed most of these injuries through passive regeneration. Threshold didn't have a healing component. His class gave him eyes, not armor. Perception, not durability.

  He followed Kira into the corridor. The dark stone folded around them. Edge Sense mapped the passage in boundary lines that were becoming familiar: the structural seams, the systemic layer beneath, the deep third layer he still couldn't read. The trial's architecture was consistent in its inconsistency, the geometry following rules his perception was slowly learning to parse.

  Ahead, the corridor narrowed. The walls pressed closer. The ceiling dropped. The space contracted around them like a throat preparing to swallow, and Edge Sense flagged something in the narrowing passage that made the boundary lines flare in a way he hadn't seen before.

  Not constructs. Not a phase-shifting floor. Something else. The boundaries ahead were dense: packed tighter than anything he'd encountered, layered on top of each other in configurations that didn't map to physical architecture. The stone walls were still stone walls, but the space between them was saturated with boundary data. Lines everywhere. Edges everywhere. The air itself divided into zones so small and numerous that Edge Sense couldn't resolve them individually.

  A boundary storm. A region of space where the trial had compressed its architecture into something approaching chaos.

  Kira stopped at the entrance to the compressed zone. Even without Edge Sense, she could feel it. The air was different here: charged, resistant, like walking into a headwind made of static electricity.

  "What is this," she said. Not a question. A demand for information from the person whose perception skill could see what hers couldn't.

  Jack looked at the boundary storm and felt his damaged body's remaining reserves calculate what it would cost to go through it. The number was higher than what he had.

  "Trouble," he said.