I. The Sky-Measuring Rule’s Calculus

  Northern Song, Bianjing, Astrological Bureau Duty Room.

  Qian Yiyan opened the purple sandalwood case and retrieved the dark, unreflective Sky-Measuring Rule.

  The ruler was two feet four inches long, its touch warm yet with a subtle, hidden chill. Its surface was densely engraved with constellations, ley lines, and ancient sigils, as intricate as a procession of ants.

  From her robe, she withdrew the "An Le" pendant and placed it beside the ruler.

  The dragon's eyes were hollow. Last night, every method of detection had yielded nothing but a chaotic sense of "void."

  But now, as the pendant drew near the ruler, a change occurred.

  The sigils on the ruler's surface began to writhe and rearrange, as if coming to life. The temperature plummeted. Frost formed on Qian Yiyan's fingers, but she did not let go. The sigils reorganized into a complex geometric pattern—six arcs interwoven with subtle curvature, appearing at first glance to rotate upon themselves.

  At the pattern's center, two symbols emerged—not written words, yet her eyes understood them instantly upon contact:

  Resonance.

  A page from her father's notes surfaced in her memory: "...Shao Yong told me: The two realms are like zither and lute. Though unseen by each other, pluck one string, and the other will hum in sympathy. This is 'Resonance.' Its principles are subtle beyond human perception, discernible only through mathematical deduction..."

  Shao Yong. Again.

  She gently placed the pendant on the ruler's "Zi" position—true north, the origin of all things.

  The moment the jade touched the ruler, the instrument convulsed violently.

  Not a physical tremor, but a "shudder" that touched the very foundations of the world. The light in the room distorted; all shadows contracted like startled ink blots. Papers on the desk rustled without wind, scattering across the floor.

  A vast, icy torrent of information flooded her mind through the ruler. Not sound, not images, but a pure deluge of "concepts"—

  Coordinates: 34.8° N, 114.5° E.

  Temporal Anchor: Night of the 7th full moon, 1st Year of Tiansheng.

  Energy Signature: Planck-scale disturbance, decoherence rate 97.3%.

  Associated Entities: Shao Yong (Kangjie), Lu Yuan (MISSING), Origin-Zero (ACTIVATED).

  Warning: Spacetime structural weak point. Recommend permanent sequestration.

  She grunted, blood seeping from the corner of her mouth. Countless concepts, red-hot like needles, pierced her consciousness. Gritting her teeth, she clung to the ruler, forcing herself to memorize every character.

  The torrent receded. The Sky-Measuring Rule fell still, its sigils restored. Only the pendant on the "Zi" position emitted a faint glow.

  Qian Yiyan slumped into her chair, her forehead damp with cold sweat. Wiping away the blood, her gaze fell upon the topographic map of Bianjing on the desk.

  34.8° N, 114.5° E.

  Her finger traced the map, stopping one hundred and twenty li southeast of Bianjing.

  The place name: Yongqiu County.

  Within the county stood an ancient Daoist temple called—

  The Temple of Primordial Heaven.

  II. Journey to Henan

  Modern, Donghai City, National Security Department Underground Command Center.

  Lu Baoyi stared at a map of central China. A red cursor was locked on a location in eastern Henan: modern-day Qi County, ancient Yongqiu.

  "Exact coordinates of The Temple of Primordial Heaven," Lin Wan pointed at the screen. "Satellite imagery shows the structure intact, but it was sealed under the guise of interior renovation three years ago and never reopened. I pulled the application documents. The signing official..." she paused, "...died of acute myocardial infarction one month after the files were archived."

  "Died?" Lu Baoyi raised an eyebrow.

  "Complete hospital records," Lin Wan's voice dropped. "But when his family sorted his effects, anything related to the temple—personal notes, photo copies, souvenirs—was all missing."

  Lu Baoyi didn't respond. Instead, he called up the section on Shao Yong from the "Chiyou" files. A blurry photocopy of a black-and-white photo showed a laboratory whiteboard covered in formulaic scribbles. In the corner, a name was circled in red pen:

  Shao Yong (Kangjie), Northern Song I Ching numerologist. Suspected of possessing trans-epoch mathematical models. Eerie correlations exist between his "Primordial Numerology" theory and quantum entanglement phenomena. During tenure as project consultant, repeatedly referenced concepts: "Celestial Tracks," "The Other Side," "Resonance Channels." Left several prophecies, three of which have materialized.

  The prophecy contents were blacked out, only the fulfillment dates visible: three years ago, two years ago, and... three days ago.

  "Three days ago..." Lu Baoyi murmured. The day of the "Shadow Devouring" in Lab Three.

  He closed the file and looked to the other side of the command center. Five figures clad in black combat gear—the "Anchorpoint" direct-action rapid response team, codename "Black Blade." Their leader, "Xingshan," mid-thirties, buzz cut, a scar running from left eyebrow to jawline. He stood like an unsheathed blade.

  "Xingshan."

  "Here." Xingshan rose, crisp as a released spring.

  "Take two, come with me to Qi County. Civilian attire, but bring Level-3 protective gear and full detection suites." Lu Baoyi pulled a silver metal briefcase from a console drawer. "Also, pack this."

  Xingshan took the case. It was heavy, devoid of markings save for a tiny, complex emblem etched in one corner—the "Chiyou" symbol, a headless axe.

  "What is it?"

  "The only intact device recovered from the accident site three years ago," Lu Baoyi said evenly. "My old man called it a 'Resonator.' In theory, it can detect and amplify specific frequency bands of... spacetime anomalies."

  Xingshan nodded without further question, turning to prepare.

  Lin Wan spoke hesitantly, "Engineer Lu, isn't it too risky for you to go personally? The Lab Three incident isn't fully understood. What if the temple—"

  "That's exactly why I have to go," Lu Baoyi cut in, his tone not louder but heavier. "If the 'Shadow Devouring' truly originated there, we're racing a clock. Every minute we delay increases the risk of contamination spread."

  He paused, eyes on the red dot on the screen.

  "Besides... I have a feeling the answers are there. About how my father vanished. About who Shao Yong really was. Maybe even about what 'the Other Side' truly is."

  III. Within The Temple of Primordial Heaven

  Northern Song, Bianjing, Main Hall of the Astrological Bureau.

  Qian Yiyan knelt on one knee before the ailing Director, Zhou Cong, presenting the pendant and the Sky-Measuring Rule's analysis. The old man, seventy-three and sallow, struggled to sit up.

  "The Temple of Primordial Heaven..." Zhou Cong coughed, his withered fingers brushing the characters on the record. "Deputy Director Qian, are you certain the Rule guides you there?"

  "The omen is clear. I dare not speak falsely," Qian Yiyan bowed her head. "Moreover, this pendant is named 'An Le'—the very name of Master Shao Kangjie's retreat in Luoyang in his later years. The confluence is unlikely mere coincidence."

  Zhou Cong fell silent for a long while. Only his labored breathing and the distant murmur of the city filled the hall.

  "Kangjie..." the old man sighed, his gaze distant. "Your father was closest to him in life. They would often discourse deep into the night here, speaking of matters far beyond the confines of the Zhou Bi or Huntian theories. Listening to them, this old man often felt as if hearing the speech of heaven itself."

  Trembling, he drew an object from his robe—an ancient bronze key.

  "Three years ago, before Shao Yong retired pleading illness, he entrusted this to me. He said if the Bureau ever faced a 'calamity not of this world,' this key could be taken to The Temple of Primordial Heaven in Yongqiu to unlock the door to the underground chamber beneath the temple. What lies beyond... might avert the disaster."

  Qian Yiyan took the key. It was old, covered in verdigris, its teeth sharp.

  "Director, did Master Shao ever say... what lies within the chamber?"

  "He said..." Zhou Cong closed his eyes, as if recalling something profoundly painful. "He said it holds the truth of the 'Celestial Track's Breach'... and also the deepest... regret of his life."

  Regret.

  Qian Yiyan gripped the key, its edges biting into her palm.

  "This official understands. I request permission to proceed to Yongqiu and investigate."

  "Go," Zhou Cong waved a weary hand. "Take Lei Huan, take capable hands. If the situation proves untenable... prioritize preserving your life. Your father's bloodline rests with you alone. Do not let him rest uneasy in the nine springs."

  "Yes."

  Exiting the main hall, she found Shen Kuo waiting in the corridor, holding a yellowed ledger.

  "Your Honor, I've traced the pendant's provenance," Shen Kuo lowered his voice. "A copy from the Imperial Repository records. The pendant is indeed Shao Yong's former possession, bestowed by the previous Emperor in the 5th year of Tianxi in recognition of his work compiling the Huangji Jingshi. But the record mentions something else—"

  He opened the ledger, pointing to a line of small script.

  "In the 7th month of the 1st year of Tiansheng, Master Shao used this pendant as collateral to borrow seven ancient texts from the Secret Archives, including Ling Xian and Annotations on the Huntian Chart, for three months. Upon return, the pendant was intact, but the Ling Xian... was missing three pages."

  "Missing?" Qian Yiyan's eyes sharpened. "Which three pages?"

  "The record isn't specific, only noting 'involves methods of covert celestial measurement.'" Shen Kuo closed the ledger. "Furthermore, the missing pages were discovered after the return. The official who verified it was... your father. He personally inspected the matter and suppressed it, never reporting it."

  Suppressed by her father.

  A suffocating tightness gripped Qian Yiyan's chest. More and more threads wove an invisible web connecting her father, Shao Yong, the Secret Archives, the pendant, The Temple of Primordial Heaven, and the calamity of the Other Side.

  And she stood at the web's center.

  "Shen Kuo."

  "Your subordinate is here."

  "You will remain at the Bureau. Continue investigating the connection between the pendant and the Archives. I need to know what Shao Yong did with those texts during those three months in the 7th month of Tiansheng's 1st year." Qian Yiyan tucked the bronze key into her robe. "I will go to Yongqiu myself."

  "Your Honor, going alone is too dangerous! At least allow this official—"

  "That is an order," Qian Yiyan cut him off, her tone brooking no argument. "The Bureau cannot be left unmanned. If I... if I do not return within three days, you may use this token to petition the Empress Dowager directly."

  She handed him a bronze token engraved with star patterns, then turned. The hem of her dark green official robe traced a resolute arc as she departed.

  Shen Kuo clutched the token, watching her back disappear down the corridor. His lips moved, but in the end, he said nothing more.

  IV. Phantoms in the Temple

  Modern, Qi County, Henan, Outside The Temple of Primordial Heaven.

  The SUV stopped on a gravel clearing halfway up the mountain. Three in the afternoon. The autumn sun slanted across the faded characters "先天观" on the temple gate, like dried blood scabs. The gates were shut, sealed with two crossed strips of paper dated three years prior, now yellowed and brittle, rustling in the wind as if ready to disintegrate.

  Lu Baoyi pushed open the car door. Mountain wind, carrying the odd scent of dry grass and old incense ash, rushed in. He looked up: Song-style hip-and-gable roof, grey tiles, ridge ornaments missing limbs. Weeds withered on the walls—a picture of desolation.

  Yet, strangely, the stone steps before the gate were unnaturally clean, as if regularly swept.

  "Xingshan," Lu Baoyi said quietly.

  "Understood." Xingshan signaled. Two team members fanned out, scanning the environment with portable detectors. The readings were normal—except for background radiation, 15% higher than the mountain average, fluctuating in an unnatural periodic curve.

  If you find this story on Amazon, be aware that it has been stolen. Please report the infringement.

  "Engineer Lu, radiation anomaly," Xingshan reported. "Peak intervals approximately... seventy-six minutes. Duration three to five seconds each."

  Seventy-six minutes.

  Lu Baoyi's heart sank like a stone. He knew that number too well—in the forbidden theories of "Chiyou," it had a nickname: The Ghost's Heartbeat. Believed to be the 'window period' for potential resonance under specific stress on spacetime fabric.

  "We're in the right place." He pulled a specialized electronic access card from his jacket—hurriedly fabricated by Lin Wan, authorized under the Ministry's "Cultural Relics Security Survey Order."

  Carefully removing the seals, he pushed the heavy gate. It groaned inward.

  Inside was a small courtyard. A central stone incense burner lay overturned, filled with rainwater and leaves. The plaque on the main hall, "Hall of the Three Purities," was faded. The hall doors were slightly ajar, dim light seeping through the crack, revealing the vague outline of statues within.

  As Lu Baoyi stepped forward, Xingshan abruptly raised a hand to stop him.

  "Wait."

  Xingshan crouched, shining a flashlight on the ground inside the threshold. In the thin dust were clear marks—not footprints, but more fragmented, chaotic drag marks, as if many slender things had crawled through.

  "Snakes?" a team member whispered.

  "Unlikely." Xingshan measured the mark width with his fingers. "Too uniform. No scale impressions. More like..."

  "Like shadows," Lu Baoyi finished, his voice grim.

  He recalled the black patches shifting under Zhang Zhiyuan's skin, the all-devouring darkness in the surveillance feed. He signaled. The team snapped into alert, weapons ready, scanners aimed at the main hall.

  But the instruments showed nothing unusual inside. No life signs, no anomalous heat sources. The radiation fluctuation had also stabilized after the courtyard's periodic peak.

  "Stay alert. I'm going in first." Lu Baoyi pushed the door open.

  The hall was spacious. Three tall clay statues sat on the altar—the Jade Pure Primordial Celestial, the Upper Pure Numinous Treasure Celestial, and the Supreme Pure Dao and Virtue Celestial. Their painted colors peeled in patches, revealing greyish clay bodies that looked eerie in the dim light.

  Lu Baoyi scanned the incense table, the murals on either side, the damaged ritual objects in the corners. Everything was normal—too normal for a temple sealed for three years.

  Then he saw it. On the floor beneath the altar, a section of floor tile shrouded in the incense table's shadow.

  The blue bricks were flat. But the surface of one tile had an unnatural "smoothness." Not polished smooth, but more absolute, as if that portion of the stone had "lost" all its texture and pores.

  Like the blank patch on Lab Three's wall.

  Like the void on the Archives' painting table.

  Lu Baoyi crouched, pulling a palm-sized handheld scanner from his pack. Aiming it at the smooth area, the screen readings went wild—

  Spacetime Curvature Anomaly: 0.0037 (Threshold: 0.0001)

  Information Entropy Density: -2.4 (Normal Range: 0-8)

  Linked Coordinates Locked: 34.8° N, 114.5° E (Matches current location)

  Linked Timestamp: Night of 7th full moon, 1st Year of Tiansheng (August 21, 1023 AD)

  "Found it..." Lu Baoyi whispered, his heart pounding.

  At that moment, his peripheral vision caught it—the shadow cast by the "Scripture of Dao and Virtue" scroll in the hand of the Supreme Pure statue. It writhed slightly against the statue's back.

  Not a trick of light.

  An actual undulation, like living black sludge.

  "Fall back!" Lu Baoyi barked.

  Before the words fully left his mouth, the shadow exploded. Dozens of jet-black "tentacles" shot out from behind the statue, lashing toward everyone in the hall!

  V. A Sword Across the Void

  Northern Song, Yongqiu County, Outside The Temple of Primordial Heaven.

  Qian Yiyan reined in her horse as the setting sun stained the western sky blood-red. Behind her, eight riders: Lei Huan and seven elite guards from the Bureau, armed with blades and bows, eyes sharp.

  The Temple of Primordial Heaven before her was more dilapidated than she'd imagined. The gate half-collapsed, walls crumbling. Only the main hall stood relatively intact, but with broken tiles and shattered windows, seeming ready to topple at any moment. Wild grass choked the approach, nearly swallowing the stone steps. The evening wind whistled through the dry stalks, a mournful sound like countless people weeping.

  "Your Honor, this place... the Yin energy is too heavy," Lei Huan said quietly, his hand on his sword hilt.

  Qian Yiyan didn't answer. Dismounting, she took out the Sky-Measuring Rule. In the twilight, the ruler gleamed dully, its sigils calm. But as she approached the temple gate, its temperature began to steadily drop.

  The closer she got, the faster it cooled.

  Pushing open the groaning wooden gate, the ruler was now icy to the touch, its surface sigils writhing and rearranging once more—this time not into a geometric shape, but a clear arrow pointing toward the main hall.

  "You will guard the gate," she told Lei Huan. "No matter what you hear, do not enter without my command."

  "Your Honor!"

  "That is an order," Qian Yiyan repeated, leaving no room for debate. "What lies within is likely not something blades can contend with."

  Lei Huan gritted his teeth, finally clasping his fists. "Understood."

  Qian Yiyan entered the temple alone.

  The courtyard was overgrown. The central incense burner lay on its side, moss-covered. The main hall doors were slightly ajar, darkness deeper than night seeping through the crack. She gripped Shou Que. The blade within its sheath trembled faintly—not fear, but instinctive reaction to powerful malignant energy.

  She pushed the door open.

  The interior was darker than outside. A few dying rays of sun pierced the broken windows, cutting bleak columns of light across the dust-covered floor. The Three Purities sat silently on the altar, paint peeled away, naked clay exposed, like three colossal corpses in the gloom.

  Qian Yiyan's gaze fell to the floor beneath the altar.

  One tile was unnaturally clean—not swept clean, but a total, void-like "cleanliness." The stone's texture, pores, even its color seemed utterly erased by some force, leaving only a smooth plane that seemed to lead into an abyss.

  Beside this "clean" tile lay scattered objects.

  Paper fragments. Yellowed, covered in writing.

  Qian Yiyan crouched, picking up a piece. The edge was charred, as if burned, yet the handwriting was clear. It was Shao Yong's script—she recognized it from the many manuscripts of his stored in her father's study since her childhood.

  A few sparse words on the fragment:

  "...Now, using the three pages of Ling Xian as the guide, I lay the 'Resonance Array' beneath The Temple of Primordial Heaven. If successful, the secrets of the Other Side may be glimpsed; if it fails, this place shall become an eternal breach. Yong knows this act defies heaven, yet where the Dao points, I would not regret it even unto nine deaths."

  Resonance Array. Eternal breach.

  A chill crawled up Qian Yiyan's spine. She recalled the word displayed by the Sky-Measuring Rule, Shao Yong's "zither and lute" analogy in her father's notes. Had Shao Yong truly tried to open a gate to the "Other Side" here all those years ago?

  And was the "An Le" pendant in her hand the... key to that gate?

  She stood, withdrawing the pendant from her robe. In the dim hall, it emitted a soft, milky luminescence, like a tiny congealed moonbeam. As she brought it near the "clean" tile, the light turned piercingly bright. Within the two hollows of the dragon's eyes, pinpricks of deepest black light appeared.

  The tile began to "melt."

  Not physically, but like a stone dropped into water. Ripples spread outward from the pendant, the tile's solidity blurring, turning translucent, revealing an abyssal darkness beneath. From the depths came a faint, indistinct hum, like flowing water or electric current.

  Within this darkness, Qian Yiyan saw... a scene.

  A strange hall: walls smooth as mirrors, ceilings lined with neat glowing panels. Several figures in bizarre black tight-fitting garb, holding strange metal implements, were confronting a writhing mass of darkness. The darkness, like living ink, was surging from behind a statue, forming tentacles that lashed toward them...

  The image fractured, flickered, plagued by intense interference.

  But she saw the face of one figure in black—a young man, unremarkable features, but eyes sharp as blades, shouting something at the darkness. In his hand was a silver-white metal device. Its front emitted a searing blue beam that collided with a black tentacle, exploding in a shower of sparks.

  People of the Other Side?

  Fighting the same "shadows"?

  Before she could ponder further, the darkness beneath the tile churned violently. The hum became a shriek. A giant, monstrous hand, formed of pure shadow, shot from the darkness, clawing for her throat!

  She leaped back, Shou Que leaving its sheath.

  The blade's light, like unrolled silk, slashed across the shadow-hand with a metallic shriek. The sword's inherent power to break malign forces erupted, blasting the hand into dissipating black mist. But the mist swiftly coalesced, forming more, finer tentacles that ensnared her from all directions.

  Qian Yiyan's sword danced like a spinning wheel, weaving an impenetrable silver net around her. Each stroke scattered shadow, but the scattered darkness immediately reformed, endless. Worse, these shadowy tentacles "devoured" the surrounding light, sound, even warmth as they attacked—she felt her strength draining rapidly, her swordplay growing sluggish.

  This couldn't continue.

  She bit the tip of her tongue, spraying a mouthful of vital essence-blood onto Shou Que. The blade hummed, silver light blazing. The intricate cloud-and-thunder patterns along its spine seemed to come alive, glowing as they writhed. This was the forbidden technique of the Qian family's "Shadow-Suppressing Sword Art"—"Blood Sacrifice, Thunder Patterns." Using one's own vital essence as a catalyst to unleash the millennia of accumulated thunderous, malignity-slaying energy stored within the sword. The cost: three days of extreme weakness, as good as crippled.

  There was no choice now.

  Qian Yiyan gripped the sword with both hands, point aimed at the ground, chanting rapidly: "Heaven and Earth, Mysterious Ancestor. Vast cultivation over eons, proves my spiritual power—Thunder, come!"

  The thunder patterns on the blade erupted with blinding electricity, washing the entire hall in stark white light. She raised the sword overhead, ready to unleash this all-or-nothing strike—

  Another change.

  From the darkness beneath the tile came a surge of unfamiliar, icy, yet profoundly "ordered" power. Then, a slender, hyper-concentrated beam of blue light shot from the depths of the darkness, piercing precisely through the "core" of all the shadow tentacles.

  It was a complex, rotating geometric symbol formed of shadow, suspended mid-air—the energy source of all the tentacles.

  The instant the blue beam struck, the symbol shattered.

  All shadow tentacles froze simultaneously, then disintegrated like ink stains losing their form, evaporating into nothingness. The hall fell silent. Only the darkness beneath the tile spun slowly, visibly diminished.

  Qian Yiyan stood frozen, the thunder-light on her sword fading.

  That blue beam... was that the means of the Other Side people?

  She looked down at the pendant in her hand. Its glow slowly dimmed, but the two points of black light in the dragon's eyes remained intensely bright. Through them, she vaguely "saw" fragmented scenes:

  The young man was on one knee, breathing heavily, his metal device smoking. He looked up, saying something to the air. His lips seemed to form the words—

  "Thanks."

  The scene vanished.

  Holding the still-warm pendant, an unprecedented mix of absurdity and certainty intertwined in her heart.

  A millennium apart, a moment's connection across light. She had fought side-by-side with an "Other Side person" whose face she could barely see.

  The pendant darkened completely, returning to its ordinary milky white. The rippling darkness beneath the tile gradually calmed. The "clean" tile regained its solidity, its surface now marked by a charred, lightning-like scar.

  Qian Yiyan leaned on her sword, her inner robes soaked with sweat. She stared at the tile, replaying those heart-stopping moments.

  The Other Side person... saved her?

  And she... saved the Other Side person?

  What was this? A jest of fate? Or some kind of... preordained alliance?

  From outside came Lei Huan's anxious call: "Your Honor! Are you unharmed?"

  "All is well," Qian Yiyan took a deep breath, sheathing her sword. She cast a final glance at the tile, then turned and walked out of the main hall.

  The sun had fully set behind the western hills, dusk deepening. Standing before the temple gate, she looked back at the silent hall, tightening her grip on the pendant in her sleeve.

  Shao Yong. Father. The Other Side. The Resonance Array.

  Every thread pointed toward an increasingly clear truth: a millennium ago, someone tried to open a gate that should never have been opened. And now... that gate was loosening once more.

  And she, and that unknown man from the Other Side, had become the first on either side of the gate to sense the impending crisis.

  VI. Data Fragment

  Modern, Main Hall of The Temple of Primordial Heaven.

  Lu Baoyi knelt on one knee, breathing heavily, the "Resonator" in his hand emitting acrid smoke. The overloaded shot had drained the device's last reserves, but it had successfully shattered the shadow aggregate's core—that self-sustaining geometric runic array of pure "informational structure" against which conventional weapons were useless.

  "Engineer Lu!" Xingshan rushed to support him. "Status?"

  "Won't die..." Lu Baoyi coughed, looking around the hall. The shadow tentacles were gone. Silence returned, save for a charred burn mark on the wall behind the statue and a faint lingering odor of ozone.

  But he knew it wasn't over.

  The "smooth" area on the floor tile remained. Spacetime curvature readings were still anomalous. The shadow creature was merely a byproduct leaking from this "breach." The true source lay deeper underground.

  "Xingshan, scan subsurface structure."

  "Already on it." Xingshan operated a portable ground-penetrating radar. The image on screen clarified. "Beneath the hall... there's a void. Depth about ten meters. Small, roughly three meters in diameter. But the material density reading inside is anomalous—not rock, not soil. More like..."

  "Like what?"

  "Unknown." Xingshan frowned. "Instruments can't classify it. Density approximates metal, but thermal and electromagnetic properties don't match any known material. And... there's faint energy fluctuation inside the void. Frequency matches the periodic peaks we detected outside. These readings... don't resemble any natural geological formation."

  Seventy-six minute intervals. Lu Baoyi checked his watch. About twenty minutes until the next peak.

  "Prep to go down," he stood up.

  "Engineer Lu, it's too dangerous! Those things just now—"

  "Those were just 'guard dogs,'" Lu Baoyi cut in. "The real secret is below. And... during that last strike, we had help."

  "Help?" Xingshan was baffled. "Who in this wilderness—"

  "Not from here." Lu Baoyi pointed at the smooth area on the tile. "The attack came from the 'other side.' A highly focused energy beam. Precision, timing—perfect. Couldn't be coincidence."

  He recalled the fleeting, blurry image in the darkness just before the blue beam appeared—a figure holding a sword, blade blazing with lightning. But it was too vague, too brief. He couldn't be sure it wasn't hallucination.

  "Get ropes and lights. I'm going down myself." Lu Baoyi's tone was final.

  Twenty minutes later, the peak arrived.

  The smooth area on the tile rippled again. Spacetime curvature readings spiked. Xingshan used cutting equipment to open a hole in an adjacent normal tile, lowering ropes and lighting. Helmet camera active, safety line secured, Lu Baoyi descended slowly into the opening.

  The underground void was deeper, colder than he'd expected.

  Light beams pierced the darkness, illuminating a cylindrical space roughly three meters in diameter, five meters high. The walls were unnaturally smooth, made of a matte dark grey material, cold and hard to the touch, emitting a dull sound when tapped—unlike metal.

  At the center of the space stood a stone platform.

  Ordinary blue stone, its surface covered in dense carvings—not words, not spells, but countless precise geometric patterns, mathematical formulae, astral trajectory diagrams. These were arranged and nested with extreme order, forming a vast, dizzyingly complex "array."

  On the platform's center rested an object.

  A palm-sized, semi-transparent crystalline slab. Encased within it was a milky-white dragon-shaped jade pendant. The carving was exquisite to an impossible degree, every scale and claw rendered in minute detail. But the most uncanny detail: the dragon's eyes were two smooth depressions—and within them now flickered a faint, ghostly blue light.

  Lu Baoyi's heart almost stopped.

  He recognized this pendant. In the "Chiyou" files, there was an extremely blurry photo of Shao Yong's listed effects. Item three was a sketch of this dragon pendant, annotated: "Kangjie token, suspected key."

  More astonishingly, the surface of the crystalline slab bore a line of minute script. Not Chinese, not English, but a symbolic language of minimalist lines. Yet the moment Lu Baoyi's eyes fell upon it, the translation formed naturally in his mind:

  "To the visitor from a thousand years hence: If you see this, the 'Resonance Array' has activated. The breach between realms will open. What lies buried here is not treasure, but evidence—evidence of the crime committed by myself and Lu Yuan in defying heaven. To halt the calamity, you must find the 'Twin Keys.' One in your world, one in the Other Side. Time is short. Shao Yong, final words."

  Twin Keys. This world. The Other Side.

  Ice shot up Lu Baoyi's spine. He jerked his head up, staring into the darkness above—from where that blue beam, the help, had come.

  Could it be...?

  At that moment, Xingshan's urgent voice crackled in his helmet comms: "Engineer Lu! Surface readings spiking! Spacetime curvature rising sharply! Something's coming through!"

  Before the words finished, the pendant on the platform erupted in blinding white light.

  Within the radiance, Lu Baoyi saw a vision—

  A young woman in dark green Song official robes, holding a long sword, stood in the decrepit temple's main hall. She looked down at a glowing pendant in her hand, then raised her head. Her gaze seemed to pierce a millennium of time, looking directly "at" him.

  Their eyes met in the light for an instant.

  Then the vision shattered.

  The white light receded. The pendant grew calm. The script on the crystalline slab faded, disappearing completely. The ripples on the tile above ceased. Spacetime curvature readings slowly returned to normal.

  As if it had all been a dream.

  But Lu Baoyi knew better.

  Slowly, he reached out to touch the slab encasing the pendant. When his fingertip was an inch away, one final line of script flickered on the slab's surface, then vanished:

  "The Key of the Other Side is named 'Qian Yiyan.' Take care."

  Qian Yiyan.

  Lu Baoyi silently repeated the name, his finger hovering in mid-air.

  From above came Xingshan's shout: "Engineer Lu! Status? Get up here now!"

  He didn't answer, only stared at the pendant, at the two points of ghostly blue light in the dragon's eyes.

  So... these were the "Twin Keys."

  One in this world, sealed here.

  One in the Other Side, a person named Qian Yiyan.

  And the two of them had just, across a thousand years, joined forces to repel an incursion from the "breach."

  What was this? A cosmic joke? Or some kind of... preordained alliance?

  Lu Baoyi withdrew his hand, tugging the safety line.

  When he regained the surface, the sun had fully set. The temple was shrouded in deep twilight. He stood at the main hall entrance, looking back at the dark hole, gripping the helmet camera that had recorded everything.

  He looked east, toward where Bianjing once stood, feeling for the first time a completely different understanding of the word "history." It was no longer lifeless archives, but a parallel timeline where a living, breathing person with a name was experiencing the same life-and-death struggle alongside him.

  "Pack up," he said quietly. "Seal this place again. Maximum security classification. And once we're back at HQ, I want every historical record on 'Qian Yiyan'—official histories, local gazetteers, any possible private journals."

  "Qian Yiyan?" Xingshan was puzzled. "Who's that?"

  "A friend," Lu Baoyi said, gazing east toward what was once called Bianjing. "A friend who... might need our help."