Disclaimer:
I do not own the Avengers, their awesome Cinematic Universe, Friendship is Magic, or Equestria Girls. Naturally, they belong to Marvel and Hasbro, respectively.

Summary:
The warlord Grogar has begun his campaign to collect the six Elements of Harmony and plunge all of existence into eternal darkness. Heroes are called to action, but can even the Mightiest Heroes of Equestria stand against the Father of Monsters, the great Grogar? Rated PG-13 for light cursing and action violence.

Devastation. Death.

As far as the eye could see, that was all that lay about. The entire might and bulk of the Wonder Bolt II lay strewn with wreckage and, far worse, dead ponies. Gladiators from the ruins of an ancient world, warriors from the destroyed Cloudsdale, both lay there lifeless and defeated. Amongst them floated a voice, surprisingly calm and almost whimsical, at odds with the carnage surroundings.

"Hear me, and rejoice," the voice said, as its speaker stepped along the decks, heedless of the pools of pony blood. "You have the privilege of being saved by the great goat himself. The mighty Grogar. This may seem like suffering... but it is..."

The speaker now came into view, a resplendent pony of long limbs and slender figure, with a pair of large, ruffled wings and a vest of black. On any other pony, her features might have seemed like classical beauty: high cheekbones, delicate muzzles, immaculate mane swept up in a prim and proper bun. But her features were lined with a cruelty, her eyes cold, and her expression one of disdain. As if she'd just caught scent of something foul.

Her name was Abacus Cinch, and she was the Herald of Grogar.

"Salvation..." she proclaimed solemnly.

Lying on the ground just by her hooves, the striped zebra Zecora groaned, unable to find the strength to rise. She'd been beaten, and so thoroughly she might be on the very precipice of death. Never in her life had she been so thoroughly mauled, and yet Grogar had done so with almost uncomfortable ease. Like swatting a fly. Unable to do anything just yet, she tried in vain to lift her head and peer down along the length of the Wonder Bolt, trying to see her liege, the Princess Rainbow Dash.

She caught sight of more of Grogar's minions, a mismatched ape-like creature, a pair of shadowy ponies with green eyes, one big and muscular, the other lithesome and hollow. Literally dotted with holes, her horn twisted and wicked. Just past them was Trixie, the other Princess, the lost, wayward daughter. She watched with trepidation as, at the far end of the carnage, Rainbow Dash was dropped to the ground. The once mighty Princess of Thunder was covered in blackened bruises, and seemed quite unable to stand.

Cinch continued her narration. "Universal scales tip towards darkness because of your sacrifice. Embrace it. Smile... for in death, you have become Children of Grogar."

Trixie grimaced at the rhetoric, unable to believe she'd even believed it, even briefly, even a little. But here she was, here they all were, and Grogar had found her. Come for her. Come for them all. A massive, towering ram of a goat, nearly twice her height, with dark navy fur and swept back, black horns. He looked more imposing than a dragon, more mighty than a bugbear, and more cunning and cruel than a changeling. At his neck hung a golden collar, with six premade indents surrounding his throat. One of which was filled, with a blue gemstone in the shape of a balloon. The Element of Laughter.

"I know what it's like to lose," Grogar stated, his voice low and gravelly. "To feel so desperately that you're right... yet to fail, nonetheless. It's terrifying. Dread it, run from it, fly from it... destiny arrives all the same. And now... it is here. Or should I say... I am."

On the ground by his hooves, Rainbow grimaced, rolling over onto her side to glare up at the goat. "You talk too much," she spat out.

He rewarded her with a kick in the ribs for her insolence, and then turned his cruel gaze over to Trixie. She knew what was coming, but she could not move, could not speak. She was petrified with fear. But not for herself.

Grogar raised up his hoof, and placed it down atop of Rainbow's head, with clear intent to crush it.

"The Element of Loyalty... or your sisters head." The Grogar made his intentions clear. "I assume you have a preference?"

Trixie turned up her muzzle and looked away primly, as if none of the carnage, least of all her much loathed sister, bothered her in the least little bit.

The great goat frowned, taking that as personal challenge, and lifted up his hoof. Instead of bringing it down on Rainbow's head, he pressed it into her back and began to apply pressure. Tough though Rainbow was, she was still only a pony, and the pressure began to build steadily, bit by bit. That tender spot right between her wings. The blue balloon gem on Grogars necklace lit up as the power of the Element flowed into his hoof, increasing his power. By a magnitude of ten, then a hundred, then a thousand. Rainbow cried out as Grogar seemed intent to crush her back into jelly, snap her spine in two. Trixie did her best to endure, but unable to look away and unable to block the screams, could not take it for even a full minute.

"ALL RIGHT, STOP!" she cried out, unable to take it anymore.

The assault ended, if not instantaneously, then at least quickly, as Grogar drew back his hoof from Rainbow Dash's back. Trixie shut her eyes tightly, holding back the tears. She couldn't. Even through all the resentment and petty pride, she couldn't hate Rainbow enough to let her die. She loved her sister too much for that.

"We don't... we don't HAVE the Element!" Rainbow coughed, spitting up blood. "It was destroyed on Cloudsdale!"

Grimacing, Trixie simply shook her head... pulling off her magicians hat... and reached inside. A moment later... a red lightning bolt of ruby crystal appear in her hoof.

Rainbow Dash, disgusted but unable to truly be surprised by her antics, sighed to herself. "You truly are the worst, sister."

"I'm sorry, Rainbow... Trixie will make it up to you..." she said, stepping forward, preparing to do what she must. Offer the Element for her sisters life.

"Your optimism is misplaced, Cloudsdale Magician."

"Well for one thing, I'm not from Cloudsdale," Trixie said with some familiar contempt. "For another, Trixie is a sorceress, not a magician. And finally... we have a hulk."

The roar that precipitated the attack was the only warning the Grogar had before something yellow and ferocious smashed into him, knocking him into the far wall. Trixie tossed down the Element and grabbed Rainbow Dash seconds before their mutual yellow friend began to tear into the Grogar, picking them up bodily and smashing them with wanton aplomb.

Easily as big as the already towering Grogar, Flutterhulk was relentless as she smashed her huge yellow hooves into his face, gut, and chest, knocking him back. For a moment, it seemed the day might yet be won, and the Incredible Flutterhulk would tear down this threat to Ponykind the way she'd dealt with the Abominable Brute or countless other threats.

Snarling, the shadowy black pony Sombra moved to assist his master Grogar. Before he could, however, a pale blue wing was held up by Abacus Cinch.

"Let him have his fun," she commanded.

Indeed, things were not as dire for the Grogar as it might have appeared at first. While the Flutterhulk could match him in raw strength and power, that was the only aspect in which they were equal. Growling, Grogar met her next blow of the hoof with one of his own, countering her strike and smacking the Flutterhulk hard across the face, drawing blood. It dripped from her nose as her gamma green eyes widened in fear.

His next few strikes were measured, powerful, ruthless. He blocked or dodged her own clumsy strikes, then hit back hard whenever her guard was down or where she was more vulnerable. He fought like a champion brawler, while she, admittedly, fought like a clumsy child. Flutterhulk reeled, totally unprepared for the relentless strikes that wore her down and especially unprepared as Grogar grabbed her body with his mighty black horns, lifting her up high above his head, then slammed her down mercilessly onto the floor of the ship. She blacked out almost instantly, a welcome reprieve from all the violence.

Coincidentally, she'd been dropped down mere yards from where Zecora lay.

Grogar grinned in triumph. Seconds later, Rainbow smashed into his side, leaving a rainbow trail behind her, but she was still weak, and unable to leave so much as a bruise. He barely glanced her way as he smacked her aside, sending her crashing to the ground. Abacus Cinch, smirking smugly, gestured with a wing, feathers flicking through the air. Stray metal fragments, animated by telekinetic power, strapped down Rainbow Dash's hooves and wings, pinning her to the floor of the Wonder Bolt, leaving her helpless to help her friend.

It was up to Zecora. Grimacing weakly, the zebra guardian clutched at the golden spear at her chest as the sharp tip sparked and spluttered weakly, trying desperately to focus the very last of her magical power.

All of her magic, all of her concentration, for one last spell.

"Ancestors aid me... one... last... time...!"

Seconds before Grogar could finish the job and end the Flutterhulk, there was a great boom, and a virtual wall of rainbow light slammed down atop of them. The Grogar and his lieutenants stumbled back as it lifted up the yellow Flutterhulk and carried them away from them, whisking them off into the distance. They were light-years away before any of them could react, and by the time the light faded and Zecora's spell was finished, there was nothing any of them could do anything about it.

Zecora caught Rainbow's eye, and nodded. Her friend, and her home, Equestria, might now be safe. Or at the very least would now be warned of the coming danger.

The zebra shaman, on the other hand...

Grogar stepped over her, glaring darkly down at the striped pony who'd cost her a kill. "That was a terrible mistake," he growled, accepting a wicked looking glaive from his underling, Ahuizoatl. Held with his hoof, he lifted it high, then brought it down sharply... right through Zecora's chest. Bright red blood blossomed forth.

"NOOO!" Rainbow cried out, struggling mightily against her restraints. "You're going to pay for that!"

Glancing idly over, Abacus Cinch flicked a single feathered wing. A final slab of metal slammed over Rainbow's muzzle, silencing her. Abacus used the same wing to hold the feather to her lips mockingly.

"Shhh."

Wrenching the glaive free, Grogar tossed it to his subordinate, who caught in his hand. The one attached to his tail, that was. Abacus Cinch took her time in reaching to collect the red lightning bolt laying on the ground, crackling with untold power.

"Mighty Grogar... please accept this gift from your children... no other being has had the might, nay the strength of will, to wield not one... but two Elements of Harmony..."

The red bolt of lightning was accepted by Grogar, who maneuvered it by hoof to the necklace at his throat. Instantly it clung into place beside the blue balloon, and a wave of energy course over him. Like any mortal pony who tried to harness it, the power of the Elements was great, and threatened to overwhelm him. But within mere minutes, by sheer force of will, the power was contained, and at Grogar's command. Two down, four to go.

"There are two more Elements in Equestria," Grogar commanded. "Bring them to me at Tartarus."

The four children bowed, Chrysalis dipping her wicked horn as she conveyed their obedience. "We will not fail you, master."

"If I might interject...?"

Five heads snapped up as a pale blue pony with silver mane stepped around them, looking distinctly nonchalant. Trixie was putting on quite the show, after all. "... if you're going to Equestria, perhaps Trixie could be of assistance? She has some experience with the locals," she added with a flick of her collar.

"If you consider failure experience," Grogar deadpanned, well aware of how her previous invasion had failed.

Trixie snorted at that, her pride definitely wounded now. "Trixie considers experience experiences!" she replied, greatly daring. Then, remembering both her plan and who she was addressing, adopted a hint more humility in her tone. "Almighty Grogar... I, Trixie, the Great and Powerful... Princess of Cloudsdale… Daughter of Firefly... do hereby pledge my... undying..."

She hesitated here, glancing over at Rainbow Dash. Her sister pleaded desperately with her eyes, unable to speak a word, but silently urging Trixie, for once, not to attempt another betrayal. Trixie, however, saw no other path forward. One hoof shifted under her cloak, reaching for one of her pyrotechnics...

"... fidelity..." she finished. And then she lit the explosive and threw it up, directly into his monstrously dark face...!

The explosion was no mere firecracker, it should've blown the Father of Monster's head clean off his shoulders, but when the smoke cleared... Grogar was wholly unharmed. And the glowing red gem on his necklace revealed why. The Element had protected him, at his will.

"Undying, was it?" he asked, with deceptive mildness in his tone. "You should choose your words more carefully."

A hoof lashed out, catching Trixie across the face and knocking her onto her back. Before she could rise, the Grogar had brought his hoof back down, right on her windpipe, crushing it. He did not even bother to use the Elements, his raw strength was alone. Just as easily as Trixie could crush an Equestria's neck, so too could he crush hers.

"Especially if they are your last," Grogar added with a dark chuckle.

"You... will... never..." Trixie rasped out, determined to have the last word.

Then, however, there came a sickening crunch.

Exit, Trixie, Stage Left.

Rainbow's muffled cries did not need to be heard to be understood, she promised death and vengeance in equal order. But Grogar was unmoved and uninterested. As far as he was concerned, he'd acquired what he'd come here for. There was no reason to stick around any longer.

"Time to go," he stated, stomping his hoof.

The Element of Laughter at his throat lit up. A wave of cobalt energy washed over the ship, sweeping the decks of the Wonder Bolt, smashing panels and destroying conduits. In moments the entire ship was ablaze, cracking apart at the foundations. Grogars Children gathered around him as he activated his second Element, and Loyalty blazed with crimson light as it opened a portal that swallowed them up. The instant they had vanished, Rainbow was free of her shackles, but she was too weak to do anything more than stumble over to Trixie's rapidly cooling body, laying her head down beside her sister. There was nothing she could do but wait to die with her.

"Sister... I'm so sorry..." she sobbed.

The entire Wonder Bolt II cracked like an egg, and debris began to scatter amongst the void as all hooves on board were lost to the cold ravages of space.

Meanwhile, the rainbow energy carrying Fluttershy whisked her away, speeding past stars and planets, angling around meteors and comets, traversing nebula and galaxies speeding its way towards a tiny green-blue speck of a planet. Equestria. And more specifically...

... downtown Ponyville, at the home of none other than Starlight Glimmer, Mistress of the Arcane Arts.

Who was currently making her way down the spiral staircase in her home towards the front door, intent to go out and purchase for herself a sandwhich. She had a hankering for something with daisies, but she'd decide once she got there. Her colleague and fellow sorcerer Sunburst trotted after her, the two deep in conversation. Something deep and spiritual.

"Seriously? You don't have any money?" Starlight asked, making sure she heard him right.

"Attachment to the material is detachment from the spiritual," he said, trying to sound sagely and sounding more like a dork. Adjusting his glasses didn't help either.

Starlight rolled her eyes. "I'll tell the fillies at the deli, maybe they'll make you a metaphysical hayburger with fries..."

"No, wait, wait, wait," Sunburst said, hurrying to her side, checking under his cloak. "Wait, I do have... uh... well it's about two hundred," he said, checking the currency he'd found in his back pocket.

"Bits?" asked Starlight, one eyebrow raised skeptically. She did, however, stop to wait for him.

"Chivs," he replied. It was an obscure currency.

"Which is?"

A grimace crossed his face as his glasses slid down, trying to do the math. "Uh... bit and a half?" Which wouldn't buy him a pack of candy oats.

Starlight sighed deeply, knowing there was no way she could, in good conscience, abandon her nerd of a friend to fight off hunger by himself. It's not like he could cook, not unless they had a book on that somewhere in the library. And even then... well, she'd seen him burn juice.

"What do you want me to get you?" she asked, feeling generous.

"Well I wouldn't say no to a..."

He was cut off as a horrible crashing noise filled the air, and both of them moved out of the way of the base of the stairs as something crashed down through the floor with the force of a truck. Something surrounded by a rainbow glow. Definitely magical in nature.

Exchanging a quick glance, Starlight and Sunburst sprang forward, the latter conjuring a ring of magical runes around his horn, the former summoning her Cloak of Levitation. It snapped around her shoulders as the two of them peered into the hole left by the strike, curious to see what had made it and if it was dangerous.

For a second, it was huge, easily the biggest pony they'd ever seen, with a dark yellow coat and bulging muscles atop of bulging muscles. But even as the rainbow glow faded, they saw a paler yellow shade and a demure, almost petite looking pony there, covered in bruised and smudges. Her mane was a pale pink, and her eyes were wide and frightened. Wherever she'd come from, she looked like she'd gone through hell. And hell was still coming after her.

"Grogar is coming," she gasped out, her voice sweet but shaking with a terrible fear. "He's coming..."

Sunburst and Starlight shared a look, the latter just as confused as the former.

"... who?" she asked.

Authors Notes:
And so it begins.

I had this story at least partially written almost three months after Infinity War came out, with Stygian as the big bad Pony of Shadows. But I delayed because I wanted to see how Endgame would shake things up. And boy am I glad I did, because if not that, then Grogars appearance on the show definitely made him a much more suitable big bad. I found another role for Stygian, however.

I'm sure some will question my casting choices, and many more will guess the ones to come, but I'm confident of my choices in the context of this story. Some more than others, but we make do with what we have.