The rumble came first.

Down on the windswept ground of the frozen Jotun Pass, the vast throngs gathered there could feel it. There was no rhythmic thumping, no steady beat to mark the sound of marching feet. It was simply vibration, raw sound and motion that steadily grew till it filled the entire valley. With dry mouths and hands tightly gripped on polished spears, the allied forces waited in grim silence as the rumble approached.

Then darkness appeared.

Cresting the final slope, a tide of black lumbered forth as the nightmare armies of Nul approached. Writhing tentacles and distorted limbs, shambling masses of bloated bodies with much too large mouths full of bone white teeth and tombstone, crushing molars, there was no words that could do these advancing terrors justice. Each and every creature was something that crawled forth from the darkest recesses of a madman’s mind, a being designed to rend apart the soul even as it rent apart the flesh. And there were so many of them. Even as the foremost ranks began their descent, more streamed in to fall in behind. The creatures were a living flood, more force of nature than army as the first thousand came into sight with ten thousand more waiting to follow suit.

The soldiers were brave. They hardened veterans, men and women who’d seen the heat of combat more times than many had seen the sunrise. But even they had never seen beings quite like these beasts, nor ever in such large numbers. These weren’t armies of this earth, so how on earth could anyone ever hope to–

“HOLD YOUR GROUND!”

All across the valley, the voice of General Ironside boomed, firm and resolute as a mountain of steel forged in the heart of a blazing star. With that one command, the front lines who’d found themselves inching back returned to their posts as their commander’s words gave new resolve to their quavering hearts. Whatever it was they faced, they would hold. Such was the duty of a soldier and such was the task that they held.

Perhaps it was the command that spurned it. Perhaps it was the sight of lines refortifying their ranks. Whatever it was, in one instant, the black tides raised their grotesque heads and howled a cry of screeching nails, bones grating, and bubbling, putrefying flesh. It was a maddening howl that sounded from a hundred thousand distorted throats as with one, very simple goal, the tides began their charge.

Even from up high in the command post, Ironside could feel the ground shake as Nul’s corrupt thundered down the pass’ narrow slope. Whatever he thought, his visage did not change as he turned to the young lieutenants at the signal array to his side.

“Signal the artillery,” he said, his voice as still as a winter pond. “They may fire at will.”

Rapid relays broadcast out, sent along spells and weavings to various outpost spread across the valley and the mountains around. In less time than it took a man to say his prayers, the orders were out and the fires of heaven rained down.

Two dozen cannons roared to life and blasted out great balls of flame, each the size of a family barn. Hot enough to slag stone, these burning stars sailed across the valley and crashed into the black tides like meteors from the sky, exploding upon impact to tear the land itself into showers of razor shrapnel even as waves of liquid fire burst forth to consume everything that lay in their molten paths.

Thousands of creatures perished with the first volley alone, blasted apart in chunks of charred ichor or vaporized back to the black mists from whence they came. Thousands more died in the second wave, and the third, and the fourth. But for every one that fell, another swooped in to take its place as grotesque demons clambered over the seared corpses of their brethren to continue the assault.

The artillery had slowed the charge, but the charge had not stopped. The darkness advanced.

“HEAVY ARMOR!” Ironside roared, spells carrying his voice to every soldier present. “POWER UP AND HUNKER DOWN!”

In rippling waves of glittering plates and glowing runes, the vanguard of the allied forces, the fully armored aura mages readied for combat. Enchanted strength brought forth massive shields of reinforced steel, each one as tall as a man and wider than two with spiked hooks firmly trust into the ground to add even more stability to its already impressive weight. From behind these shields, the aura mages channeled, bringing their resonant magick to the utmost as she planted feet into the ground and pressed shoulders into the shields.

“KEEP THEM STEADY!” Ironside called as ice blue eyes locked on the charging tides, still rent by the relentless barrage of flames, but always clambering closer. “YOU’VE GOT A HUNDRED PACES LEFT! EIGHTY! SIXTY! FORTY! TWENTY, AND–”

It was like stopping an avalanche with bare hands. Even with their heavy armor and enchanted strength, the vanguard shuddered as they were bodily pushed back for a good several paces. The weight was immense as thousands of creatures clambering for blood and meat hurled themselves against the shields’ spikes in a mindless attempt to breach their cover. For a moment, several spots along the line shuddered as the demons almost broke through.

Almost.

Planting feet firmly once more, runes glowed bright as the vanguard redoubled their efforts and held their ground.

“SPEARS! FORWARD!”

Glittering silver tips lowered and thrust, sliding between the gaps of the shields to impale whatever corrupted flesh they could find. Creatures howled and died as the Equestrian blades stabbed into the ranks over and over again, ripping down the first wave of creatures before reaching out to those behind.

But even so, the darkness pressed forwards and the allies fell back.

“Lieutenant,” Ironside called. “Is the Triad ready?”

“Warming up as we speak, sir,” the soldier answered. “They should be ready in about… ninety seconds.”

“Sounds good,” the general nodded. “Then send the word out to the Third, Fifth, and Seventh. Tell them to open the gates.”

Hesitating for only a moment, the lieutenant dispatched the orders. With a glow of broadcasting runes in their spell arrays, the command went out, and the soldiers moved.

The line gave way. Bulging inwards from the pressure, three points in the line broke apart and allowed Nul’s armies to flood through. Surging on ahead, the fel beasts attempted to turn and tear at the exposed flanks of the soldiers behind the wall. Only, there were no exposed sides to be had.

At each of the fractures, full columns of heavy armor aura mages stood ready with massive shields set up all the way down the valley’s length. Though the demons hacked and clawed, they could land no more than a few passing swipes as the press of the throngs from behind pushed them further down the steel-clad channel. The darkness pressed a thousand paces inwards, two thousand, as three passes a hundred paces wide apiece filled to the brim with the abominable hordes.

All as the generals intended.

Three great cannons, each the size of a barnyard silo, lay directly in the line of those surging breeches as they charged their massive payloads, Though lying dormant since Morghulis and the Days of Darkness, mana conduits as thick as a man's limbs now glowed with brilliant, silver light as the Triad roared to life.

Solid lightning, dense as stone and heavy as lead blasted forth in a condensed, paper thin wave along those channels. Where the lightning met beast, beast disappeared. Ten thousand demons instantly vanished along those columns and well beyond, reduced to little more than crackling mist as the gale force how of thunder trailing along that slicing blade of electric dispersed them to the four winds.

“CLOSE RANK,” Ironside called, his voice echoing dully in the Triad’s aftermath. “CLEAN IT UP AND RESUME POSTS.”

With no demons left to contend with, the vanguard resealed the breach and surged forward, gaining back each and every pace they’d given as the lines of spears cut ichor-stained swaths through the dark tides. Behind those ranks, the aura mages closed rank as well, not facing the oncoming armies, but on the ones still trapped inside. Hundreds and thousands of demons, those closest to the impregnable walls, had survived the blast, and there was no way they would be left amidst the allied armies. With weapons set to the grim work, it took mere moments for the steadily closing ring to wipe their stain from the face of the earth.

“Breaches sealed, sir,” the lieutenant dutifully reported as the field responses came in. “The push has brought us back to the starting position.”

“Very good,” Ironside grunted. “How long till the Triad can fire again?”

“Cool down and recalibration will take approximately an hour. We can charge another shot thirty minutes after that, or we can use our reserves to fire within five.”

“No, tell them to hold on to the stores,” the general commanded as he continued to survey the field. Even with their maneuvers and the countless already blasted back to the infernal pits, the black tides looked not a shade lighter. Nul’s armies continued to pour through the pass to refill the crackling furloughs carved by the arcane blasts. In a matter of minutes, it’d be like nothing had happened at all.

“How are the gunnery crews doing?” Ironside asked as he turned his attention now to the rain of fire that had continued unabated since the start.

“Still within operational bounds,” the lieutenant reported, “but overheating’s starting to take a bigger mana drain. Estimates have output efficiency at approximately seventy percent.”

“Not good enough,” the general frowned. “Tell them to lower the angles fifteen degrees and hold fire till my mark. It’s time for Lacero to do his thing.”

Though the howls of the demons had not changed, they seemed for a moment to grow louder as the sound of thaumaturgical artillery fell silent across the battlefield. However, it was only for a moment, because a new sound quickly rose to take their place.

Launching from various airports constructed throughout the mountains, the unparalleled aerial might of the Griffon Imperium armada took flight. Dozens of bombers the size of Stallion class transports, each with its own cadre of sleek, deadly fighters, winged their ways to their positions over the battlefield with synchronized precision as they began to lay down their payloads.

From wide berths, winged Griffon legionnaires tossed large casks onto the crowds below, the crushing weight that smashed monsters underneath merely a small bonus to the actual purpose of the drops. As the casks shattered, they did so with explosions of not fire or thunder, as one would expect, but of super fine powder that hung thick in the air. Though a breeze should have dispersed the payload, spellcraft enchanting the dust held in suspended in place as blooms of fog-like shrouds appeared all over the battlefield.

“Lacero sends his regards,” the lieutenant called. “Ready when you are.” At the news, Ironside allowed himself a small smile of pleasure.

“Open fire.”

High up in well constructed towers, Equestria's elite marksmen opened fire and sent powerful lances of flame shooting out towards the dark masses that continued to press below. As always, those searing bolts cut through targets like a hot knife through butter, but that was once again, just a bonus. The real treat was when the flames encountered one of those blooms of dust. Just one touch, just the faintest brush of enchanted fire, and…

Boom.

The air itself ignited as the dust combusted with enough force to shame whole factories of fireworks. Suspended in the most lethal range possible, each explosion focused its deadly force to tear apart demons in gouts of black mist and inky blood. Fire rained, air burned, and the armies of Nul were cut to charred ribbons time and time again.

Yet no matter how much they burned, no matter how many countless died, the darkness did not recede. Every gap in their ranks were quickly filled with more grotesque beasts as the pressure of their ranks on the vanguard continued ever forward.

“Lieutenant,” Ironside called as the smile faded into its natural, stony planes once more. “Tell the artillery to run at three quarters speed in alternating rhythm with the Griffon dust drops. I want those guns running at optimal efficiency to get as many shots as possible, got it?”

“Sir, yes sir!”

As the sound board worked to relay the orders, Ironside’s visage darkened into a thunderhead of grim determination. If it had only been a theory before, it was certainly a very clear reality by now.

There was no way to win.

No matter what they threw at the dark tides, there would always be more to come in their place. Their numbers were quite literally infinite, and nothing could outlast eternity.

Fortunately, they didn’t have to. They just had to last long enough, to keep these eldritch abominations contained long enough for those seven youngsters to do their job. All they had to do was hold on and drag out this war of attrition until victory came from a different front. They didn’t have to win. They just had to survive.

Of course, surviving against these sort of odds was about as easy as outlasting a seven day hurricane on a driftwood raft. Not odds he relished, but one played with the hand he was dealt, did he not?

And so, with ice blue eyes harder than the permafrost they fought on, Ironside settled in for the longest battle of his life.