Rutile felt like there was a spider in her brain.
It seemed like the best description she had for the crawling sensation that make her feel like something was watching her, and doing so with disapproval. She'd never put any stock in the horseapples of alicorns ascending after death--dead was dead, and everypony and everyone would eventually cross the River of Souls and see whatever was on the other side in their own time--and so she'd, in turn, never felt that her actions were being weighed and measured by a force that she couldn't see. Even when she occasionally sent a prayer to Mi Amore Cadenza, that was more foxhole mentality than true belief...
But right now? Something felt like it was making itself at home behind her eyes, thin legs skittering through her grey matter and making her hairs want to stand on end. And she wanted it gone, as soon as possible, especially because whatever it was made a headache bloom behind her eyes whenever she brightened her horn to compensate for the continued lack of light; the crystals were still burnt out in this section, and so she wasn't surprised when she saw dark smoke starting to resolve into equine shapes.
These ones were a little more distinct, and as they formed, hints of different colours started to be seen in their smoky bodies. Three in total, one had a hint of bronze, another a dash of aquamarine, and one a brush of pink. It was the last of those who spoke, breathing out, "Cryssstal...?" in a raspy hiss.
Talking was new, but Rutile raised her cannon-wearing leg all the same. "I'm starting to get real tired of fighting off monsters, so if you've got more words, use them carefully."
"Wait!" The bronze one surged forward. "We're not your enemy, cryssstal unicorn. There'sss no need for usss to come to blowsss."
"Crystal unicorn?!"
Rutile ignored the outburst from Tundra, her cannon still trained on the shadow and smoke. "Really? Because we already had a close encounter with some creatures that looked a lot like you."
The aquamarine one shook their head, making the suggestion of a mane ripple. "Thossse were jussst shadesss. Fallen remnantsss. We're true umbrum, and after thousssandsss of yearsss down here, we're not interesssted in picking a fight with the firssst new faccce."
"Umbrum? Root--"
"I know what umbrum are," Rutile cut Tundra off. "My parents told me the story of Sombra and Radiant Hope."
She'd already suspected that that was she'd been fighting before, but she found herself believing them that those hadn't been true, whole umbrum. These three were much more like what had been described to her as a foal.
"Sssomepony who remembersss the old ssstoriesss?" The pink umbrum rippled with excitement, and voids where eyes should have been still managed with widen with delight. "Then you know that umbrum can choossse to be more than monssstersss. We don't have to fight."
Tundra was radiating terror, and Rutile could feel her pressing close, their fur intermeshing. She still kept her eyes trained on the trio. "You've been here for thousands of years, you said."
"Yesss. We've been locked--"
"In the inner chamber." She bobbed her head at the hall past the umbrum. "Is there an alicorn there?"
All three went still and silent for a long moment. Then the bronze one spoke, quietly. "You ssseek the Cryssstal Empressss."
"Yes. And if we're not enemies, then you know what would prove it?" She angled her head slightly, to indicate Tundra. "Helping us get down there to set her free."
The aquamarine one seemed to bristle. "She'sss the reassson this placcce hasss been sssealed. Why we were sssealed in with her, asss a ssside-effect." The bristling smoothed, and they made motions of a breath they didn't need to take. "But... forgivenessss isss part of change, isssn't it? No longer keeping old grudgesss."
They all looked at each other, and each gave a nod, before the bronze one spoke up again. "We'll help you, cryssstal unicorn. If. You do sssomething for usss firssst."
Rutile raised a brow, finally lowering her cannon to the floor. "What do you want?"
The pink one turned sombre. "Our mother."
The spider in Rutile's brain ceased its skittering, and the headache started to clear. "...Keep talking."
Glass shards bounced off Tundra's shield as the case exploded. The crystal that'd been within hit the floor and skidded a short distance, without a single chip or scratch.
Once the debris settled, Rutile headed for the hunk of quartz, dodging Tundra's attempt to grab her short tail and telekinetically pull her back. "Root, this is way too dangerous. The umbrum--"
"Are the ancient enemy of the crystal ponies. An enemy so old, they predate the Exodus." Pale blue magic seized the stone, and she rotated it in the air as she took in every angle. "A lot of things have changed, Tundra. And as the last crystal pony left, I think I get a say in whether to keep that grudge."
"You're..." Tundra came up to her side, watching the quartz as if it may leap out and bite her. "They... were right...? You're a crystal?"
Rutile snorted and gave a sardonic smile. "You really never noticed, historian?"
"My specialty is archo-tech!" she blurted defensively. Then, looking over the mare with fresh eyes, she continued, "Unicorns can have a wide range of spells, including emotion-based ones, so you being an empath didn't seem too strange. And you don't look..."
"Sparkly?" Rutile offered, then rolled her shoulders in a shrug. "Either that part's a myth, or there's a trigger for it I've never found. The actual signs are subtle, subtle enough that my own parents thought I was just a mutant at first." Her ears drooped a bit as she sighed. "Maybe there's the potential for more, lurking around in pony genetics." She glanced at her mark. "But trust me, right now I know for certain that I'm the only crystal pony in the galaxy."
At those words, the quartz shuddered in her grasp, and the blue started to be consumed by impenetrable black. The crystal jerked, Rutile's magic hold breaking and it soaring down to slam into her chest. She could faintly hear Tundra calling her name as her legs gave out, knees slamming into the floor, but she was too consumed by the pain to respond.
"Finally my waiting pays off..."
Her veins burned like lava had been poured into them, and the transparent bandage over her gashes was shredded as black crystal spread over them instead, providing their own seal. More crystal spread over her burned leg, until it had covered it from hoof to knee. Only once the transformation had stopped and the pain had faded to a dull ache did she move, shakily rising with a groan and finding Tundra there immediately to lean against as she got to her hooves.
Rutile looked down, and found the heart-shaped stone embedded in her chest, right below the base of her throat. She tentatively moved her coated leg, finding that it flexed just as easily as flesh, and found herself breathing a dark laugh at the irony. Well, if she hadn't looked like a crystal pony before...
"...Root?"
"I'm okay." Rutile tried to give a reassuring smile, but was pretty sure it looked more like a grimace. "If this used to be an umbrum, there's not much left now. Hope they'll still take this as me holding up my end of the bargain."
Dead was dead. She stood by that. But some things died in strange ways, and did so more slowly than others. There was life in the crystal, but not much. Maybe whatever just happened would stop the remainder from crossing over, and maybe it wouldn't, but at that moment, Rutile didn't care.
She was close to seeing her expedition, and her vow, done, and so she said the only thing she could. "Let's get moving."
"You're back!"
The umbrum circled Rutile, and her leg twitched with a desire to raise the cannon again to ward them off, but she suppressed it. She let bronze, aquamarine, and pink inspect her in turn, and it was the last who drew their head close to her chest to stare into the quartz, watching the light within pulse with Rutile's heartbeat. "Thisss isss all...?"
The bronze one, instead, looked directly into Rutile's eyes, and she stared back, not flinching away at all from the empty gaze. Whatever they'd been searching for, they seemed to find it, as they eventually nodded. "You've done your part, cryssstal unicorn. We'll free your empressss, and free ourssselvesss."
Rutile smiled. "Good. I'm glad we could come to an understanding."
As she trotted down the dark hallway, all three umbrum stuck close, speaking to one another in excited whispers in a language that Rutile didn't understand.
Tundra trailed behind, and her dread was thicker than the shadows.