The Imperial Shrine World of Garibaldus lay deep in the heart of Segmentum Ultima, far from the reach of Holy Terra even without the Cicatrix Maledictum obscuring the Emperor's light. It was a lush and verdant world of great forests and rolling plains, towering mountains and deep, blue seas. A myriad of foot-trails and stone-laid roads carefully meandered through the natural environment, leading to and from uncountable shrines and temples dedicated to Imperial Saints and the many roles and faces of the Emperor worshiped across the Imperium. The few permanent inhabitants lived in a small number of walled-off Hiveworlds, which mostly served as points of entry for trade and transport.
Billions of pilgrims from across the Segmentum would journey here to wander the dark forest trails and remote mountain paths to secluded places of worship, yet the untouched wilderness offered no danger to them. No beasts, pests, or plagues inhabited this world's forests and plains, only docile grazers, colorful birds, and skittering arboreal foragers. In truth, this world had been settled long before the Imperium, before the Old Night extinguished Humanity's progress. The planet was extensively terraformed and seeded with many species of Terran-born flora and fauna by its original discoverers, all genetically engineered to serve humanity in all things.
Over the millennia of neglect and disregard, however, the domesticated ecosphere had slowly reclaimed the world from its human creators, becoming wild and self-sustaining yet retaining a deep indifference and benevolence to Mankind. Adherents of the Imperial Cult began to venerate this unique world, seeing it as both a gift from the God-Emperor and as a template for what a world completely and totally subservient to Humanity would be like. As such, the planet's Ecclesiarchical authorities went to great lengths to preserve the strange natural order that had arisen on Garibaldus, seeing any undue interference or exploitation of the land as sacrilegious desecration of an Imperial relic. The few Hive-cities that did already exist acted as great reservoirs for Imperial teachings and holy relics, brought from near and far by pilgrims and holy men alike.
Since time immemorial Garibaldus had acted as a remote beacon of Imperial culture and faith, and now more than ever it served as a light in the darkness of Imperium Nihilus. At least, it had until a combined force of Death Guard and Word Bearers, each led by their respective daemonic Primarch, descended upon the idyllic world without warning.
It was the planet's holiness that attracted them, a plan proposed by the Urizen himself. The Primarch hoped that a sufficiently blasphemous act of desecration against such an ancient yet relatively vulnerable holy site like Garibaldus could be offered up as a sacrifice to the Dark Gods - who had been strangely silent as of late.
The two traitor legions assaulted the many fortress-worlds and orbital defense platforms which surrounded the Garibaldus System, built up over dozens of centuries to protect the holy Shrine World from assaults just like this. The assaulting Traitorous forces swelled their ranks with daemonhosts and hordes of maniacal cultists, sending wave after wave of their expendable ranks while keeping their elite Astartes troops in reserve. Lorgar and Mortarion had expected these inhuman wave attacks to be enough to overwhelm the beleaguered defenders, seeing as they were cut off from Imperium Sanctus and unlikely to receive reinforcements or aid from the forces of their Corpse-Emperor upon Terra. They were correct in assuming no aid would come from what remained of the Imperium… yet nonetheless, the faithful defenders of Garibaldus did receive aid.
"Peregrinus Militarum Sancti Athmos" is what they had come to be known as: an amorphous, decentralized, loosely organized military force spread across Imperium Nihilus. The "Peregrines", as they were often called, were not so much formed as they were hastily pulled together in an ad hoc fashion after the Great Rift cut off countless worlds, guard regiments, and naval fleets from the Imperial command structure. Like headless snakes, the forces of the Imperium stranded in Imperium Nihilus were left aimless and alone, some entrenching in place and awaiting salvation from Imperium Sanctus while others wandered aimlessly across the void in search of sanctuary. When it became clear that what remained of the Imperium would not be able to reclaim the "Dark Imperium" even with the miraculous return of the Primarch Guilliman, the starved and depleted regiments and fleets which had not succumbed to oblivion were forced to improvise.
Without the monstrous bureaucracy of the Adeptus Munitorum to supply them, the forces of Imperium Nihilus had to establish their own logistical networks and supply chains, slowly and pain-stakingly mapping out local systems and sectors to procure the resources necessary for their continued survival against the onslaught of daemons, mutants, heretics, and whatever else crawled out in the shadow of the Astronomican. It was a slow and arduous process, but planet by planet, system by system, older methods of communication were established. Eventually, these local networks began to overlap and connect to one another, forming a decentralized web of ad hoc supply chains and command structures stretching loosely and messily from the Halo Stars and Galactic Core to the Ghoul Stars and Eastern Fringe.
Yet this improvised network of battlefleets, guard regiments, and forge worlds remained nothing more than an autonomic reaction to a hostile environment, unable to self-organize or pursue a broader goal beyond immediate survival. In a sense, it was still a headless snake, just larger and more well-fed. All of that changed, however, when a ship full of deserting guardsmen crossed the Nachmund Gauntlet. Fleeing from the wrath of the Inquisition and spreading out from Vigilus on any ship that was available, the survivors of the Siege of Leprus acted as seed crystals upon finding and embedding themselves within the aimless forces of Imperium Nihilus.
While aboard the Saint's Chariot, the battle-hardened Guardsmen fleeing from Leprus had begun to share their experiences and forge them into a new way of thinking, one adapted to their new lives as deserters and renegades stranded beyond the Rift. The brutal and pragmatic tactics and strategies they had developed to repel the siege-experts of the Death Guard's first company and survive without a coherent command structure, all while cut off from outside reinforcements, found fertile ground amongst the leadership of Imperium Nihilus's military forces, many of whom had found themselves in similar circumstances. Yet it was not only strategic experience that the renegade guardsmen carried with them; along with it came an ideology of self-reliance and rejection of Imperial overreach, spurred on by their ruthless treatment at the hands of the Inquisition. With the presence of the Inquisition beyond the Rift minimal at best, word of their atrocities spread uninhibited among a populace that already felt abandoned by the Imperium at large. It was not as though the victims of the Inquisition's persecution were in short supply; with a certain chapter of Astartes in the nearby Elara's Veil sector being an infamous target of their ire.
Yet if all these guardsmen had to offer were strategic advice and anti-Inquisitorial agitation, they would have simply been absorbed into the ever-churning ranks of the nameless masses fighting to survive in the cold, dark void beyond the reach of the Astronomican. Instead, they brought something even more valuable than tactics or doctrine:
They brought word of a saint. One that had torn through the entire first company of the Death Guard, humbled a champion of the Dark Gods, performed countless miraculous healings, and had just willingly followed them into the abyss of Imperium Nihilus.
And so, the Free Militant Order of Saint Admus - the Peregrinus Militarum Sancti Athmos, answered Garibaldus's call for aid. While the fledgling organization was still in its infancy, having spread relatively little and their name far from widely known, the Shrine World's pilgrimages had acted as a conduit for them to establish themselves in this part of the galaxy. Indeed, this would be the first time Guardsmen would be fighting under the title of Peregrinus, and they were determined to earn a reputation for that name in battle. Their modified doctrines were especially adept at repelling the unorganized assaults of the Death Guard's thralls, and their zeal seemed to be more than a match for that of the Word Bearer's heretic cultists. They were identifiable by their standard guardsmen armor painted in silver and white, adorned with either an orange-gold stripe, the icon of teal horns, a green beast's paw, or any other of a myriad of heterodox symbols which had come to be associated with the legends of Saint Admus - itself just one name amongst countless variations.
Mortarion stood with arms crossed, staring down at a dull, gray fortress world from the bridge of Lorgar's flagship, the Trisagion. It was a monstrous battleship dating back to the final days of the Great Crusade, and even accounting for chaotic corruption it was in remarkably good condition. Mortarion would have normally embarked on an excursion like this upon his own plague-ship, the Endurance. However, with the Terminus Est taken out of commission for the time being, Mortarion chose to keep his personal flagship in reserve to defend the Scourge Stars.
Mortarion had mixed feelings about being in the company of his brother and fellow traitor. While they were united in purpose and in fealty to the dark gods, the Word Bearers practiced in a far more… intentional way than the Death Guard. Strange incense and burning oils filled the air with a smoky blood-tinge, though not enough to mistake for a Khorne-worshiper's gore-soaked stench. Even beneath his noxious rebreather, it bothered his perforated sinuses… though what really troubled him was having to rely on another legion at all. It would take some time to recover from the losses they'd sustained both in the Plague Wars and in the humiliating defeat at Leprus, so for the time being he accepted the Word Bearer's assistance, albeit reluctantly.
"Status report, Commander Gothax." Mortarion said into one of the ship's built-in vox communicators.
A hazy, holographic projection appeared on the viewport, revealing a Death Guard Lord adorned with the heraldry of the 3rd Plague Company, "Mortarion's Anvil". With the crippling of the veteran 1st Company and the disappearance of their Commander, Typhus, Mortarion had elected to summon the 3rd Company as his retinue due to the 2nd Company being needed to both help replenish the 1st company and defend their realspace holdings from any counterattacks by neighboring Ultramar.
"The loyalist dogs are resisting, but we've already successfully besieged three of their bastions. The planet should fall within the next two weeks." Gothax wheezed.
"Two weeks?" Mortarion said. "You are fighting planetary defense forces, not the Imperial Fists. Is two weeks truly necessary to break the defenses of mere unaugmented humans? I deployed your plague marines because the common rabble of cultists and plague zombies failed to overwhelm them. Is this all you can truly manage?"
"The enemy no longer consists of mere PDFs, it appears they were reinforced by a regiment of Imperial Guardsmen." Gothax said. "They are proving… difficult to dislodge."
"Define difficult for me, Commander Gothax." Mortarion said, wheezing with frustration.
"Our plague-weapons are not proving as effective as they normally would be. Guardsmen infected with pathogens that should kill in a matter of minutes seem to continue fighting for hours or even days before perishing. One of the Word Bearers' Dark Apostles has suggested it may be some kind of faith-powered healing ward, but it is unlike anything we've encountered thus far." Gothax said.
Mortarion rubbed the rough, parchment-like skin on his forehead. He was aware that the Imperium had developed treatments for some of Nurgle's poxes with limited efficacy, but those were intensive procedures which required a great deal of resources and logistics to utilize, not something a band of Astra Militarum stragglers could cook up by themselves. He also knew of the Orders Hospitaller using faith in a limited capacity to heal; however, the reports made no mention of the Adepta Sororitas having a presence in the system.
"A new form of healing ward? That sounds fascinating…" Lorgar said, emerging onto the bridge of the Trisagion. "I would much like to capture some of these guardsmen alive to… 'study' them. We may be able to pervert their misguided faith into a weapon of our own." He said, rubbing his chin.
"So, they are more resilient than the average guardsman… what of it? Are you not Astartes of the 14th Legion?" Mortarion said, ignoring his brother's intrusion.
"The guardsmen are engaging in a type of warfare that counteracts our typical combat doctrines. Underground tunnels, hit-and-run attacks, elastic defensive lines with hidden caches and kill zones… it does not seem to be in line with the corpse-worshippers' usual tactics. We are advancing… but more slowly than we anticipated. Their tactics… they are like the ones employed upon… Leprus" Gothax said, his wheezing voice carrying a hint of trepidation.
Mortarion's milky eyes widened, and his face bore a grave expression.
"...but that is not all. Some of the guardsmen bear unique insignia… antlers, painted upon their armor. They rallied their men with prayers… to a new saint." Gothax said.
Mortarion's grip dug into the metal console of the vox-caster.
"A saint?" Lorgar said, a smug grin on his face. "Seems the corpse-emperor has chosen a new puppet. What, pray-tell, is the name of this slave to the Golden Throne?"
"They call her… Saint Admus." Gothax said.
"Another lamb to the slaughter, leading the hapless flock to the abattoir." Lorgar said. "Wait, actually… that name sounds familiar… Mortarion, doesn't that sound similar to-"
Lorgar stopped dead when he looked upon his brother's half-rotted face, seeing nothing but unholy rage simmering within the Primarch like a rancid boil.
Once Mortarion descended upon the defenders, the entire system lasted less than 72 hours.
Beneath the smouldering, blood-red skies of Garibaldus, Mortarion spread his fetid mothwings across the air and landed atop a scorched hilltop just outside of a now-ruined hive city. A retinue of Word Bearers stood watch outside of a small temple, scorched with unholy flame and desecrated with perverse rites. The air was filled with the noxious odor of chemical defoliants and biophagic plagues, masked by choking plumes of toxic smoke arising from the innumerable fires raging across the once-verdant shrine world. The seas boiled, the forests burned, and the mountains crumbled beneath the overwhelming bombardment of chemical, biological, and conventional weaponry Mortarion's fleet was still carpeting the surface of Garibaldus with.
Mortarion approached the doors of the sullied temple, but they swung open before he could reach them.
"I don't understand it…" Lorgar said, emerging from the dark interior. "A thousand shrines desecrated… millions of faithful pilgrims slaughtered… an entire paradise dedicated to the accursed corpse-emperor despoiled beyond recovery… and still the Gods are silent." Lorgar rubbed his smooth scalp in contemplation. "Something must be distracting them. But what could possibly occupy the Gods to such an extent?"
"Luckily for the both of us, I have a more practical method of extracting information." Mortarion said.
He turned towards a procession of Plague Marines and Nurglite zealots behind him, carrying with them a line of ragged and sickly prisoners taken from the nearby hive city. Their faces were sunken and ghostly pale, their skin clammy and green like seaweed festering in the sun. He'd made sure to have them infected with a viral strain that would sap their life force and cause them unceasing agony but keep them alive and conscious all the while.
"Gothax, have you extracted anything useful from the prisoners yet?" Mortarion said.
"Unfortunately, it seems none of the guardsmen we've tortured so far were present on… Leprus." Gothax said, spitting out the name like a bitter poison. "They simply learned of their tactics from this 'cult of Admus'."
Mortarion winced. He had forbidden the scant survivors of Leprus from speaking the daemon's name, so it was unknown to all but a few within the Death Guard. He wanted to keep it that way.
"Keep interrogating them." Mortarion said.
"My lord, if I may… I have a question." Gothax said.
Mortarion gave him an impatient look.
"Well? What is it?" Mortarion said.
"This world was a verdant paradise, ideal for the seeding of Nurgle's gifts of decay…" Gothax said, looking out at the burning horizon. "...I cannot help but wonder why you have chosen to destroy it, rather than present it as a gift to the Plaguefather."
"The ashes will make fertile ground for Nurgle's rot all the same. Entropy comes, dissolving all whether by decay or by fire." Mortarion said, turning to Gothax. "Now let me ask you a question, commander. Has the Plaguefather sent you a daemonic emissary to express his disapproval? A Herald? A Plaguebearer? A Nurgling, even?"
"N-no…" Gothax said.
"Then what right do you have to interpret Nurgle's will? Above me? Or do you wish to join ill-fated Typhus, who foolishly believed he was uniquely favored by the Plaguefather as well?" Mortarion said.
"Of course, Lord Mortarion. I shall not question your judgment again." Gothax said, his head hung low.
Mortarion wheezed laboriously through his mask, his worm-eaten lungs not used to such intense outbursts.
"It seems we share a breakdown in communication with our Empyrean patrons." Lorgar said.
"I know Nurgle's will." Mortarion growled. "That daemon… she blasphemed the Plaguefather, brought ruin to his works, and humiliated his sons… my sons!"
"About that…" Lorgar said. "I still cannot put it out of my mind that guardsmen would worship a daemon… as a saint. It's quite unprecedented. Do you think… that our target may not be a daemon at all?"
"Are you suggesting she really is one of the corpse-emperor's saints?" Mortarion said.
"It's a possibility." Lorgar said.
"No… our 'father' is many things… hypocrite among them… but above all else, he is a supreme narcissist. He would never allow one of his slaves to falsely proclaim not just allegiance to one of the Four, but kinship." Mortarion said.
"You make a convincing argument…" Lorgar said, rubbing his chin ponderously. "But I cannot help but think we are missing something… if only the Gods would answer my prayers."
"Lord Mortarion!" A plague marine shouted, shoving his way through the crowd of bound prisoners.
Mortarion and Lorgar turned to him, and saw he was dragging along a heavily wounded guardsmen wearing white armor, his shoulder plate adorned with a stag's horns.
"This one was deployed on Leprus, according to one of his comrades who ratted him out. All's we had to do was pluck that one's eyes out and he squealed like a Grox, heh. Milksop." The Plague Marine said, making a sound halfway between a gurgle and chuckle.
The marine shoved the bound guardsman to the ground, landing face-first onto the dirt. The daemon Primarch looked down on the mortal with passive contempt, like one would gaze upon a fly that had landed on their food. The injured and sickly guardsman looked back at him with a hint of defiance, just barely masking his exhaustion and fear.
"What do you know about the events that transpired on Leprus, worm?" Mortarion said, his wheezing voice reverberating like a low growl. "Depending on your cooperation, I may lessen the suffering you experience as your internal organs are liquified and your soul is claimed by Nurgle's rot."
"Go to Hell, daemon." The guardsman said, weakly. "The Emperor protects my soul… even now."
"Oh, we have experience dealing with men of faith." Lorgar said with a smug grin. "There are a number of rituals to take care of that pesky 'Emperor's protection' your kind so cherishes. It's much more fun to make them renounce their false god all on their own, but we even have ways of continuing the 'extraction' process… post-mortem."
The guardsman stayed silent, his withered frame shaking slightly.
"Take him away." Mortarion said. "Extract what you can from him… then throw him in the pits with the others."
The Plague Marine began to drag the guardsman back into the throngs of other prisoners, the wounded soldier struggling to put up much resistance.
"Wait!" The guardsman said. "You're looking for her, aren't you?"
Mortarion raised his hand, commanding the Plague Marine to stop.
"Bring him here." Mortarion said.
The Plague Marine shoved the guardsmen to his knees, backing away so he sat alone in the Primarch's shadow.
"You were on Leprus." Mortarion.
"More than that." The guardsman said. "I saw her. With my own eyes."
Mortarion raised his chin, Lorgar turning with an intrigued expression. The guardsman had their full attention.
"I saw her alright." The guardsman said. "I saw her heal your demon-poxes with only a touch. I saw her slaughter your godforsaken Plague Marines like cockroaches. I saw her tear through tanks, Terminators, and Dreadnoughts like a blade through grass. I saw her send that fat bastard Typhus running like a newborn babe, Emperor knows what became of his sorry self. Now she's out here in the dark with us, biding her time, gathering her strength, and soon enough she'll be back to finish what she st-"
Mortarion's scythe cleaved straight through the man's neck, sending his severed head tumbling to the ground. His hands shook with rage as he gripped the hilt of his weapon, his face contorted into a furious scowl.
"Mortarion what the hell are you doing!?" Lorgar shouted. "He was in the daemon's presence at her last known location. He could have known where she was going, or her current whereabouts!"
Mortarion wheezed heavily, his diseased lungs laboring against his uncharacteristically raging temper.
"You were just bragging about being able to interrogate souls, were you not?" Mortarion said, his breathing still ragged.
"There are rituals that must be carried out beforehand. Preparations that must be made. It is not as simple as plucking daisies from the ground. For all his negligence, our half-deceased father can be quite covetous when it comes to human souls." Lorgar said. "It can still be done… but it will require expending some of my daemonic contracts. Luckily for you, I have many."
Lorgar approached the deceased guardsman, shoving Mortarion aside and outstretching his hands. He closed his eyes and began to chant guttural verses in the Dark Tongue, the glyphs inscribed on his skin beginning to glow with infernal light. His eyes opened, and like embers in the wind the symbols lifted into the air and swirled around him, forming chaotic patterns and circles which seemed to twitch and slither with unnatural life. The writhing graphemes encircled the dead guardsman, seeking out and latching on to whatever scraps of warp-residue remained of his soul.
"For one chosen by Nurgle, you are showing a surprising lack of patience, brother." Lorgar said.
"I demonstrate patience every moment I am in your presence, brother." Mortarion said.
The two shared venomous glances, but further argument was avoided as Lorgar's ritual bore fruit. The tendrils of glyphic magic dredged from the corpse a wispy, ethereal silhouette, struggling against taught cords of golden light that resisted the daemonic forces. The guardsman's soul - more of a hollow shade, held precariously between the material and empyrean planes - writhed and gasped like a drowning fish. Lorgar's hands trembled as he attempted to keep the soul trapped in this unnatural state.
"This will require… my full concentration… Mortarion, interrogate the soul before it slips away!" Lorgar said.
"The daemon… the saint… where is Tadmushtum?" Mortarion said.
The writhing soul's illuminated eyes darted back and forth as its head contorted in unnatural angles, its mouth flapping wordlessly before it began to echo something approaching speech.
"S-sear... g-gant… K…Kelly…" The soul reverberated. "S-spoke… to… saint's… knight…"
Saint's knight? Mortarion thought. A mortal champion?
"What did the knight say?" Mortarion said.
"S-sought… ancient… wisdom… sought…" The soul said, the outline of its form beginning to waver uncontrollably.
"I can't hold on for much longer!" Lorgar said through gritted teeth.
"Sou… sought… Baal." The soul uttered, just as Lorgar's ritual magic was severed.
With a brilliant flash of light, the soul vanished, vaporizing the daemonic tendrils holding it in place. Lorgar and Mortarion shielded their eyes from the holy radiance, the rays of light inducing a nauseating discomfort in the daemon Primarchs.
"Sought Baal…" Mortarion repeated to himself. "The daemon is headed to Baal."
"Baal…" Lorgar said, catching his breath as he recovered from the strain of the ritual. "So, the daemon is headed towards the homeworld of the Blood Angels… what would a daemon be seeking there?"
"We must prepare an invasion force." Mortarion said. "I intend to find out."