The self-refined Kindling from the Adeptus Astronomica watched the mechanical chassis cross the threshold of the dungeon and offered a shallow bow.
"Iron Man Axion. By the will of the Emperor, Lord Guilliman and I have awaited your arrival. In accordance with His divine intent, we are to entrust an artifact to you. As part of this compact, it is hoped you will assist in ensuring the continued survival of the human race."
The machine cast a clinical, discerning gaze at the psyker, whose frame radiated erratic fluctuations of empyrean energy.
"How do you propose to prove that the current residents of this Imperium are the legitimate successors of humanity?" Axion asked. "From my perspective, they are little more than a collection of hominid abhumans. Their biological baseline, social configurations, and existential modalities differ radically from the Human Federation of old. Even their genomic sequences show significant drift."
The psyker manifested no outrage. He simply turned toward the Primarch.
"Lord Regent."
Guilliman, momentarily caught in the tectonic implications of Axion's words, shook off his distraction at the psyker's call. He reached into a specialized satchel at the hip of the Armour of Fate.
He withdrew a singular piece of micro-machinery. It bore a passing resemblance to a key, yet its surface was a dense web of negative-space filigree and exposed logic-circuits. At its heart sat an unidentified crystal, pulsing with a faint, golden luminescence that governed the rhythmic flow of energy through the device.
"This unique key is the price of our accord," Guilliman stated. "The past you seek is contained within. However, you must uphold your side of the pact: the human race must not be permitted to fall into extinction."
"I cannot verify the authenticity of history through a single source," the machine replied. "Validation requires cross-referencing multiple data-streams. Should the records prove consistent, I will recognize the treaty as binding and ensure the continuity of the extant human population."
The machine's logic appeared to align perfectly with the revelations granted to the psyker. Even Guilliman showed no sign of offense, as if every word spoken had been anticipated by the Master of Mankind.
The psyker nodded, his voice a dry rasp.
"Then the accord is struck. The Imperium shall serve as your ally in unearthing the histories lost to time. All is for the preservation and future of mankind. The signatories of this pact are the totality of the Human Race and the Iron Men."
Axion's optical sensors spun at high velocity before locking into stasis.
"Sapient Prime Axion accepts the terms. A non-time-limited protocol has been confirmed and logged within the Core Intelligence Repository."
The psyker allowed himself a thin smile, then looked to Guilliman.
"It appears the timing is precise."
…
At that exact moment, at the Mandeville Point of the Sol System, a gargantuan mechanical fleet tore its way out of the Warp.
The Titan's Spear and a host of vessels unrecognized by any Imperial registry immediately triggered every void-augur and alarm in the Imperial Navy. The Solar Fleet, charged with the sanctity of Terra, scrambled toward the system's edge in a state of high-alert panic, interposing themselves before a mechanical armada that rivaled the scale of the Great Crusade's expeditionary fleets.
The Dawn of Fire, lingering in orbit, immediately accelerated to join the Solar Fleet in the system's outer defense perimeter. Aboard his flagship, Lord Commander Solar Leontus stared at the long-range pict-feeds, identifying the Iron Man fleet instantly.
"Is this to be the day the Imperium ends?" he whispered.
He had never imagined the Imperium would eventually be forced to face these mechanical reapers. The harrowing reports from the Pacificus war zones, the cold, clinical casualty counts that consisted of nothing but mounting death tolls, sent a shiver through his soul. He knew the Solar Fleet possessed superior ship-grade quality compared to the Tyranid bio-fleets, but they were hopelessly outnumbered.
According to records from Segmentum Pacificus, colossal Hive Ships and bio-cruisers were systematically dismantled by the hundreds within mere minutes of engagement. The Solar Fleet boasted dozens of capital ships and several Emperor-class Battleships, yet combined, they would likely fail to endure a single coordinated volley from the fleet before them.
However, the predicted slaughter and the firestorms that would have choked the stars did not manifest.
Upon clearing the Mandeville Point, the massive mechanical fleet executed a disciplined maneuver, coming to a dead halt in the outer void and falling into an ominous silence.
Moments later, a joint order issued by the Lord Regent and the Captain-General of the Custodes rippled through the vox-channels, commanding all Imperial forces to stand down. A collective breath of relief swept through the fleet. The Solar Fleet drifted back, maintaining a wary vigil over the silent mechanical giants, while other reinforcements en route to Terra were ordered to hold position.
…
Having re-established a link with the collective, the Emissary chassis beneath Terra completed its data-synchronization with Axion's primary consciousness aboard the fleet. With his prime intellect now in direct control, the machine took the key from Guilliman's hand.
"Now," Axion stated. "You will inform me of the nature of this key."
Though Guilliman had followed the psyker's guidance into the Emperor's private sanctum and retrieved the key from a drawer within a personal scriptorium, the artifact's specific function remained a mystery to him.
The psyker pointed to the key in Axion's grasp.
"This key provides access to a secret laboratory the Emperor concealed within the Webway. Within it lies a journal penned by the Emperor Himself, a record containing the history and the truths you pursue."
Axion's electronic eyes flickered. "Locating a single laboratory within the labyrinthine expanse of the Webway?"
The psyker nodded. "The Emperor conveyed to me that during His research into Webway technology, He spent a protracted period within its depths. Using certain technologies, He carved out a sub-spatial pocket, a warehouse of sorts, to facilitate His work. His journal, which serves as His research manual, was left within that sanctuary."
"Ultimately, when the Webway collapsed into instability, a tide of daemons and traitors overwhelmed the deeper reaches. The Emperor could never return to that laboratory, and He Himself was subsequently confined to the Golden Throne."
Guilliman stood in stunned silence, hearing these hidden truths for the first time.
"And how am I to locate a laboratory within the Webway?" Axion asked. "The Iron Men do not possess the inherent capability to breach the Webway gates."
The psyker looked at Guilliman with a cryptic expression.
"Within the Webway, the key will resonate as you approach the laboratory. Its energy is tethered to the unique seals the Emperor placed upon the threshold. As for breaching the Webway... I suspect Lord Guilliman has a solution in mind."
As Guilliman's expression shifted to one of realization, golden psychic fire suddenly erupted from the psyker's body. The light was holy, saturated with a warmth that defied the cold damp of the dungeon.
The mortal did not scream. Instead, a look of profound, blissful release washed over his aged features.
"I have fulfilled the task. The Emperor's mercy is manifest. All sacrifice is for the glory and continuity of the human race. For the Master of Mankind, may His light endure forever."
As the divine radiance flickered out, nothing remained on the stone floor but a small mound of ash. The robes of the kindling lay atop the pile, scorched but intact.
Guilliman stepped forward in silence, kneeling to gather the ash within the folds of the robe.
"You gave everything for the Imperium," the Primarch whispered. "Your name shall be etched into the annals of our history. Your kin shall walk in the pride of your shadow. This, I vow."