There were many realms.
Some eerily similar yet vastly different to others across the cosmos and between the boundaries of time. Underneath it all, Hell reigned, ever growing, expanding, reaching wherever the seeds of evil could be planted. Across invasions of these vastly different planes, the shadow horde's rank and file would see recurring units. Chess pieces among the armies of Hell, fitting molds that had proven effective in the past.
One of these chess pieces had become a powerhouse mainstay, modeled after an ancient demon whose wrath outlived body after body, to fulfill a promise made to a warrior in times long forgotten to history. This demon was heralded as being the first in a never-ending battle with Humanity that Hell had been locked within for eons. Beyond death, his vengeful spirit would find flesh anew to battle Humanity's finest warriors, and when the behemoth was felled, he would only resurface stronger than before.
In his honor, lesser idols had been crafted in his image. They would fill out ranks and take leadership roles where due. These idols were known by many names to many peoples. Some knew them as Cyberdemons, crafted in tandem with humans lulled into serving Hell's will. Some knew them as Tyrants, wardens and jailers of the black soul pits of Babel.
The original...was named the Harbinger.
His battles against the Earth realm's mightiest warrior, the Doom Slayer, were told as legend throughout Hell. One of few who did not fear him...so much as he respected his eternal rival. Their first clash came during the First Age, atop a monument to Hell's power, and the demons' first victory against humanity, the Tower of Babel. It once stood atop the lost moon Deimos in one of many variations of the Earth realm, but was reduced to rubble over the course of their fateful battle. The Harbinger was granted another chance to battle the Slayer during the original Mother Demon's campaign, in a treacherous Hell temple...his challenge echoed throughout the accursed halls, "Watch Your Step…" Many moons later, he was resurrected in another Earth realm's UAC facilities on Mars, and battled a far more powerful Slayer in the Lazarus Labs during the prelude to the largest-scale Earth invasion Hell had ever attempted.
Time and time again, the Slayer had emerged victorious. Yet this only strengthened the Harbinger's tenacity, his will to overcome the strongest warrior he'd ever face - Humanity's champion.
After he was slain yet again during the Mars incident, the Harbinger was brought back through the experiments of cultists from another realm.
The original Cyberdemon was born anew...but this time would be different.
This time a rage broiled through his body that perhaps rivaled that of his eternal nemesis. He laid waste to the cultists, stole and outfitted himself with equipment initially designed for Aggadon Hunters, and then began his own unholy crusade.
While all of Hell knew of two that bore the accursed Slayer's scent, the nature of nigh infinite dimensions and realities meant that more existed across the aether; at different times, under different circumstances.
The Harbinger sought to bring as many as he could hunt to ruin.. And from quarter to quarter, domain to domain...he succeeded. For every Doom Slayer, Marine, "Guy", Flynn, Reaper, Joan or otherwise he found and defeated across the realms, ever his power grew...swift and unrelenting. Many battles were close, many weren't. The disparity between these results became thinner and thinner as the Harbinger hunted his eternal nemesis throughout the cosmos. Now, though, the Harbinger's hunt would have to be put on pause...
...for his services were called upon yet again.
The bloody container of Cultist design that housed the remains of the Spider Mastermind sat immobilized in a great altar, built into the ancient city of DIS, reconstructed after it was destroyed in a climactic battle during the First Age. The building was dimly lit by arcane torches, blood and gore gathered in the corners as biofuel to steady the Dread Widow's recovery. Above the altar the ceiling was open, with Watcher Eyes placed all about the city so that she may peer upon her subjects...and the current object of concern.
"Look into the sky, Harbinger," the Aranea Imperatrix commanded in a dull, tired tone.
Several moons and locales from conquests past were present in the red sky of their eternal hellscape, as they always had been...but now an unfamiliar, alien planet hung in the skies of Hell. In horrible contrast it burned a searing blue, teeming with crackling radiation. Its visage was a blight, and brought with it a sense of creeping dread...for its size dwarved any other celestial body in the sky, as if it had been feeding on many worlds before arriving on Hell's doorstep.
Spewing from it in great droves were putrid comets of flesh and fluid. They hailed across the far reaches of the hellscape, rapidly mutating and corrupting wherever one struck. Demons that were not obliterated by a comet's impact were irradiated and mutated into more powerful, vicious forms, and immediately lashed out and slaughtered those near who hadn't been graced by the comet's corruption.
"I call upon you, Harbinger, to seek out the source of this wretched eyesore which so boldly enters our domain," the Dread Widow explained. "Not even Titans are immune to its poison. To think the Khan Maykr's blunder would have allowed us access to Urdak...but bring with it such troublesome...consequences. I am certain you can feel it in the air. The dimensions are unstable...and the state of all realms only worsens with the experiments of new invaders. They are fools."
Save for blood bubbling in the Mastermind's tank, and the crackling of dim torches, their conversation held a silent audience. But the Harbinger felt the presence of his kin lurking in the shadows of the chamber.
"We believe much of the dimensional interference is coming from operations on a certain Earth, our last...unsuccessful target. It might interest you to know that our failure was partially in fault to Him currently residing there."
The Harbinger's eyes furrowed, and smoke blew from his nostrils. Not one of his targets across Creation had proven to be easy game...but none had fought with the same ferocity of Hell itself that the Doom Slayer had in battles past. The prospect of encountering his nemesis in apex form again after all this time...it brought a smile to his face.
"We don't currently have the resources in place to attempt another full-scale invasion of the realm...but the fractured barrier between worlds has made travel once again feasible. The invaders have already made several breaches into our realm with varying degrees of success. Find their base of operations...and put an end to their meddling."
"Their hubris will be their undoing, Dread Widow," the Cyberdemon affirmed, turning his back to her and travelling though a grand slipgate conjured by several Summoners.
"Pray it will not be yours, as well, Harbinger. And be wary...for the Slayer is no longer alone."
Droves of demons stepped from the shadows to follow the Harbinger of Doom, who'd felled great cities single-handedly in times past, and who had finally returned following a campaign against the Accursed One.
The Aranea Imperatrix was left to ruminate in her chamber, bathing silently in the lifeblood of the damned that was just enough to keep her alive. Perhaps it was the subject she'd been reincarnated from, but the circumstances surrounding the world she'd come back to intrigued her endlessly. How she longed for the body she'd known so briefly before the Doom Slayer ripped it away from her. She could still see through the eyes of her subjects, what few some-million remained on Earth after the invasion. She felt the pain of each and every one of her most direct offspring, the Arachnotrons, as they were maimed and toppled by the scourge of Hell.
And perhaps, most of all, she felt the swelling fear in her subjects' hearts as abhorrent reckoning hung in the skies of their domain, turning them against themselves as a Great Poison spread throughout Hell.
"That is not dead which can eternal lie," she quoted, calling upon a swathe of memories gained from her rebirth.
"And with strange aeons...even death may die."
