The rotting pony had no eyes; only glowing blue spots visible between plates. The same couldn’t be said of its mouth, the gaping orifice dripping with black fluid and ringed with sharp teeth. A low moan bubbled out between those teeth, agonized and terrible. One could almost hear the suffering of the pony it had once been in the gurgles of the monster it had become. Was that pony still conscious enough to register pain?

Shining Armor hoped not.

The Prince of the Crystal Empire — at least insofar as one could even be a “prince” of the war-torn, outbreak-wracked wreck the Empire had become — reared up on his hind legs, one forehoof flying toward the thing’s face. A snarl of pain erupted from the infected’s warped throat as his claws dug into its face, gripping it tightly. A moment later, and the creature’s head had been crushed against a nearby wall, ichor erupting from between the gaps in Shining Armor’s talons.

Ponies aren’t supposed to have claws. A small voice hissed from the back of his mind. As usual, he did his best to ignore it.

Several more infected were charging down the tunnel at him, each one of them warped by the Fleshmetal Plague in a slightly different way. Some bore thick plates of crystalline chitin, others had equally-crystalline horns that jutted from their twisted foreheads. All former citizens of the Crystal Empire, innocent crystal ponies whose only crime was succumbing to the Fleshmetal Plague.

Unfortunately, those innocent creatures were between him and the exit. More importantly, they were between his innocent, uninfected companions and the exit. Thus, they had to go, and the only way that would happen was through the application of force. Lethal force.

A lance of concentrated magic slammed into the ground amongst their ranks, impaling one of the horned infected and killing it instantly. Shockwaves of violet energy radiated out from the magical projectile, launching all the rest of the creatures into the air, rendering them incapable of retaliating. The effect wouldn’t last for longer than a few seconds… but a few seconds was all he needed.

A firearm slid off of his back, enveloped in the violet glow of his telekinesis as he drew a bead and held the trigger. Unlike the flintlock weapons that ponykind sometimes found amongst its more martially-inclined allies, this rifle had been “borrowed” from (read: pilfered from the butchered corpses of) the other group of alien invaders that had decided to set up shop in the Crystal Empire. And the rifles those invaders carried could fire a lot more than just a single shot between reloads.

The roar of the weapon firing flooded the tunnel, the sound bouncing between the crystalline surfaces and generating a deafening racket. Not many of the projectiles hit home — the firearm’s recoil kept throwing off his aim — but its sheer firerate meant that they didn’t need to. By the time the magic within the lance ran out and the suspended infected collapsed to the ground, all the ones with horns had been slain, green ichor spraying from the gaping holes blown in their fleshmetal hides. He stowed the weapon, drawing a short sword as the remaining infected surged forward-

A flash of brilliant scarlet light rose from one of the infected creatures, tearing up whole sections of the cave floor. It lifted Shining right along with it, flinging him backward.

As he sailed through the air, he took note of a cluster of short, stubby crystals jutting from the forehead of the infected up front. Seems the infection was smart enough to realize that the infected with obvious horns made for equally-obvious priority targets, and had gotten the bright idea of giving some of them horns that didn't actually protrude from the head in order to catch its victims off-guard. Not that it would matter; let it never be said that Shining Armor couldn’t think on his feet.

His forehooves closed around a support beam, his momentum swinging him up and over the horizontal support, right back the way he came. Another blast of that same red-tinted energy streaked down the tunnel toward him, but this time the infected’s aim was way off. It hadn't expected him to move so fast. They never did.

Because ponies aren’t supposed to move that fast.

“Shut it.” Shining Armor hissed under his breath as his telekinesis drew a scavenged sword from its sheath. By the time the infected spellcaster started charging up another blast, Shining Armor had already landed, his hooves coming down with force that would have given Applejack’s buck a run for its money as his sword buried itself in the thing’s forehead, killing it instantly.

The remainder surge forward. When he drew the sword out of the body of the infected he'd just slain, only the hilt came out; the blade remained buried deep in its body, snapped off at the base of the hilt. No matter; he still has his hooves.

The seconds blurred together as Shining Armor fought, his body moving almost on automatic as it tore into the foes before him with deceptively-restrained savagery. He was thoroughly desensitized to the sensation of spore-laden blood and sticky slime splashing on his coat by now, but even so, his mind still finds the ease with which he was holding off the infected more than a little surreal. Just three years ago, he’d been on the receiving end of the Changeling Queen’s mind control, completely at her mercy; in the end, he had to be rescued by his sister and wife, the two ponies he wanted to protect more than anything else in the world — and on his bucking wedding day, no less. A little bit after that, he’d tried to stand up to Sombra… and promptly had his magic sealed and his battered body tossed aside, dismissed as too weak to even be worth killing. And then Tirek came along and ate his magic. And then he got captured by Queen Chrysalis, and had to be rescued again. And then there was the whole debacle with the Storm King’s invasion.

A part of him used to hate himself for those failings, for being so weak. Used to wish that he had the strength to fight back against things like that, to hold his own against those threats the way his sister and their friends could. But now…

The last infected fell, torn clean in half by my taloned hooves. For a long, long moment, he just stood there, practically knee-deep in dozens of bodies, slime and bile and ichor dripping off of my skin. His wish had been granted; he’d just proven it. And yet, the victory rang hollow.

Maybe it was the knowledge that this strength is completely unearned, how everything about his new body feels wrong, unnatural — like some fundamental part of it wasn’t meant to exist, and the universe can tell. Maybe it was the way the flowing, electric-blue fibers that had replaced his mane and tail didn't flow quite like a real mane or tail would. Maybe it was the terrified gazes that he could already feel boring into his back, as if he was suddenly on the same level as the dreaded Sorcerer-King Sombra, at least in the minds of the half-dozen survivors gathered behind him.

You’re not a pony. Not anymore.

Or maybe it’s that tiny little voice in the back of his mind, the one that keeps reminding him that ponies can’t charge into unarmed combat against dozens of opponents at a time and walk away unscathed, that they can’t run on walls, that they can’t bucking double-jump. The voice that keeps him up at night and adds fuel to his nightmares when it doesn’t. The voice that leaves him wondering if the small group of survivors he’s escorting to safety have every right to be looking at him that way.

“The way out is clear.” He sweeps the detritus from the battle aside with his telekinesis, clearing a path for the crystal ponies behind them. The infection requires direct bodily fluid contact to spread, but the fact that all the infected in this corridor are dead doesn’t make their spines, claws, or teeth any less sharp. The more he can do to minimize the risk of accidental infection, the better.

There’s no response; just deafening, dread-filled silence. He glanced back at the crystal ponies behind him, huddled behind an outcropping of glittering rock. He'd guessed right; a number were staring at him with barely-disguised horror. One was even throwing up. He couldn't see any signs of disease, Fleshmetal Plague-related or otherwise; apparently seeing the battle was enough.

“Look, you don’t have to come with me, but you can’t stay here." Shining Armor told them, hoping that a little logic would be enough to overcome their understandable fear of him. "The infected know that you’ve been holed up down here now, and they’ll be back.”

That got them moving. They emerged from cover, following behind Shining Armor as they all trudged along the trail he’d carved through the heaps of infested corpses… though they gave him just as much of a berth as they gave to the mutilated bodies. Honestly, he couldn't blame them for that. His particular strain of the plague may not be contagious, but that didn't make the changes it brought about in him any less disturbing.

“It killed them,” One of the survivors — the one who was puking earlier — murmured. “All of them. Just like that.” Shining Armor would have let his head droop from shame and self-loathing if that didn’t mean looking at his own white-and-grey hide. His face was still untouched, aside from a few scraggly scars marring his once-handsome face, but everything else from the neck down was covered in a white-and-grey 'bodyglove' of sorts. At least, it just looked like a bodyglove on first glance; closer inspection would reveal that it was actually his skin, replaced with the same metal-like material that the Fleshmetal Plague had been named after.

“Autumn Gem, I don't think we have the luxury of being judgmental about Shining Armor’s conduct at that juncture.” One of the other survivors interjected.

Shining Armor nodded, even as he focused on the walls, unable to bring himself to look any of the survivors in the eyes. He could still barely stand to look at himself in mirrors, but the fragmented reflections he couldn't help but notice in the crystalline growths weren't too much of a problem. They weren't too frequent, and when they happened, he could still pretend the glimpses of ichor-drenched fleshmetal he saw in the reflective crystals weren't glimpses of his own body. “They… they were beyond saving. All we can do for them is put them out of their misery.”

For a moment, Autumn Gem was silent, the only sound the soft clopping noise of hooves on rock as they all left the veritable slaughterhouse that tunnel had become behind.

“Then what does that say about you?” She finally asked.

“…that’s a damn good question.”

Author's Note

So... this little brainworm crawled into my head, and wouldn't come out until I dealt with it. I have endeavored to write this crossover in a way that can be understood by people who don't play warframe, but in case you're still confused, here's a little context.

The "Fleshmetal Plague" is a strain of the Infestation that has taken root in the Crystal Empire. Unlike the original infestation, this strain has been tinkered with, which is why it's nanospores aren't airborne. It can still infect ponies — any ponies, though alicorns are particularly resistant to the plague — through direct bodily fluid contact, such as the sort caused by bites or claw scratches. The name the ponies have given it refers to the semi-metallic growths infected individuals develop.

As to what Shining Armor has become... he's something that's appeared in the lore far more recently: a Protoframe. He's been infected with another variant of the Infestation, a modification of the Helminth strain used in the creation of warframes. As a result, he's essentially a Pony/Warframe hybrid, granted the biology and ability of a warframe but still retaining his identity and (most of) his equinity. The converted Twilight we see in the prequel to this fic could also be considered a Protoframe, though she ended up veering more toward the "warframe" side of the hybridization than Shining did.

And as for who did this to them? That's the "invaders" Shining Armor makes reference to, the Grineer. These guys were once slaves to a certain ancient human empire, but broke free of their shackles after their old masters kicked the bucket. They then immediately became just as cruel and oppressive as their former masters were, and set their sights on conquering the solar system. They have a bit of a history of tinkering with the Infestation, which is how all these new strains of the Infestation came into being. I won't say more, to avoid spoiling reveals in sequels to this fic that I have planned.

One of the biggest inspirations was Frames Of War, which planted the idea of ponies being hybridized with Warframes in my head. Another, less obvious inspiration was actually Together Forever; while not being Warframe-centric or even a crossover, it depicts a similar situation in which Shining Armor is saddled with a different body and none-too-happy about it, and both feature an inner voice reminding Shining of his inequine condition.

And yes, the Incomplete tag is not a mistake. I have plans on continuing this, though I intend for it to be relatively short (three or four chapters).