It's probably just that it takes so long that it won't happen in a single battle, but over many many battles.
In the meantime, I have some writing. For the sake of brevity and explaining certain spawn creatures (such as the re-named "Uberspawn" and the Degenerates - which were supposed to have legs dang it,) I'm going with Armok using an army of long-dead champions from across the ages to assail the underworld and destroy The Detective herself, as the underworld is the single constant across oh so very many holds.
So long ago. So very long.
Ancient heroes fought great evils, and that evil triumphed. It birthed legions forged from the spirits of dwarves both living and dead that tore through the continent of West Everoc, slaughtering many and waging stalemated wars throughout. As this horde fell upon the southern glacier claimed by the dwarves of Syrupleaf, a shift had occurred in the winds of magic. The god of gods observed them. Soon, after years of terror and blood, the evil creatures finally bested the ancient heroes.
Heroes like Sirrocco, Nemo, Tehsid, Daeren, and Royal W.
And many countless other unsung and forgotten heroes of many races, all died at their claws and their maws. Theirs was a sacrifice of blood for their people, and all were welcomed into the grand hall of the allfather Armok.
However, now many were the monuments that would see no further use, and warriors who would no longer be able to spill the blood of others, and this god of gods was displeased.
Armok instructed the gods of this world to beat the overlord of this great evil into submission, and lock it away with the other demons of the underworld. And so it was.
The wars continued of course, and many desperate folk began at last to flee. Men, Elves, Dwarves, Goblins. All fled in all directions. The elves took to the skies on the backs of their flying friends, the Men by sea, the Dwarves and Goblins making treaties of convenience to cross great expanses of the underdark, beset on all sides by horrors unimaginable.
Many of these brave refugees and pioneers died. But even more arrived in a new land, a new world... East Everoc.
The lands were lush, untapped, and exceedingly deadly. Blood that smelled of burnt bacon fell from the skies and clouds of roiling death choked many forests and plains. There were the undead of course, but that was nothing new to the peoples of West Everoc. But the giant beasts, hostile tribes of animal men, and a race of angry and tall bearded menfolk who lived in frigid climes and mountains proved to be daunting foes to face. But, nonetheless, they prospered.
Centuries passed, and while West Everoc was only just beginning to claw its way back to civilization, an old foe was seen crawling from the mountain caves. Cruel alters raised in the center of dark hollowed caves running with magma formed the basis of sprawling hives of the evil. Someone, or something, had unleashed it. And so war came to the world again on a great scale. But where the ancients had turned to machines and magma to face these foes, their descendants had decided they could trust not their walls and traps.
As the wars raged and many died, great powers also stirred. Time and space were crushed before the might of even the Allfather, and the divines could only lend their aid to those they supported as the great Corporations that arose from the ashes of West Everoc went to war against eachother. Warped flesh, towering monsters, necromancers, and alien warriors formed the initial waves of the conflict, and soon genetically engineered horrors and advanced weaponry were pitted against flying machines and stalwart professional warriors wielding the arms of an ancient age.
Others would be dragged into this second war. Small companies and nations, manipulated by a great schemer who ultimately met his end to his own hubris and the carefully crafted machinations of disloyal underlings.
New heroes would come from these great and terrible wars as a result. Dauros, Vanya, Draignean, Urist, Hans, PaintBrushTurkey, Lefton, and perhaps the most important of them, Fischer. Some like PaintBrushTurkey, Vanya, and Draignean are now venerated as great heroes centuries still later. Others, however, Dauros and Fischer, are regarded by some as gods. And there is some truth to this.
As for some, Even in Death they still serve.
In the centuries following their passing, the hordes broke. some turned on themselves, as if the dwarves within these monsters had regained control and lashed out against those who had not. Others dissolved as they suddenly appeared directionless. In a matter of decades, hordes of tens of thousands, were reduced to barely greater in number than the infantry companies of many human kingdoms.
Unbeknownst to all, Armok had finally be able to unleash upon the great demon his mightiest champions in a great torrent of doom. She who struck the killing blow being perhaps the foe who hated her most in the remaining scraps of recorded history from so long ago. With the thrust of a pike, the demon was no more, and Armok made this champion of champions the new protector of her descendants in the beardkin. TO the others, they were granted their right to a final rest in his halls, or to become gods themselves.
The threat of the great devourer, all at once, collapsed. New larvae were born warped and mutated, and other dark creatures and mad wizards would take both dead and living spawn and warp them together, while still others ran loose in the caverns, growing to immense scale feeding on the massive beasts within.
They had gone from the stuff of region-spanning wars, to just... Well, a fact of life like any other wild beast. Albeit one that could sometimes amass sufficient numbers to attack fortified settlements and level smaller ones, for a time.
Before long, the peoples of the land were expanding again and counting the remains of the great corporations among their ranks, and this time no hordes of demons would deter them. Ours is but one such tale of these new waves of expansion.
Ours is the tale,
of [NAME TBD]
It's not the best prose or anything, but is perhaps the best shorthand I could do as well as advancing the story of what happened as breifly as possible, while also referencing other things important to the backstory.
This basically assumes that Joseph is indeed dead due to him being a touch too cocksure in his countermeasures and loyalty of his underlings, Holistic is dead (that is, Armok had empowered Fischer to essentially remove Holistic from existence himself because he thought it'd be more entertaining than just unmaking her with his big ol hammer,) and her hordes are now leaderless, Fischer is the patron saint/god of the dwarves (and I'll say Dauros can be considered a lesser deity of War and Fortresses and Vanya remembered as a hero by the dwarven people,) the Time war is over, and we're several centuries past Spearbreakers. The barbarians are also being retconned into an unnamed hostile tribe of humans.