Laments of the Dimension-Stranded

Rainbow Dash galloped through the cave, whipping to the right as she changed direction. She leapt over a stalagmite, landed hard on a sharp rock and yelped in pain when it penetrated deep into the soft part of her hoof. Her body kept galloping persistently despite her objections. She had no control over her legs or wings. She tried utilizing her sapphire pendant to levitate her own body to physically stop herself, but it didn't work. When she attempted to establish a magical connection with the enchanted gemstone, it didn't reciprocate. It was if her voice had been silenced.

"Goddamn it, Dash! Stop!"

Rainbow could hear Vincent's desperate shouts echoing through the gigantic cave system. It was as convoluted as a changeling hive and equally as dark. The only light sources were sparse groups of mystical crystals growing from the walls that emitted a faint blue glow.

She passed forking path after forking path, swinging left and right rapidly. Rainbow wasn't unfamiliar with arduous exercise, but she was always able to pause if an unforeseen problem were to arise. She was hungry, thirsty and injured. Her heart was pounding in her chest like drumsticks against drums. Despite being an undeniably athletic pony, Rainbow had reached the furthest extent of her physical capabilities. Yet despite her brain screaming warnings to stop, her body disobeyed, moving at maximum speed.

Her hooves scraped against the rock floor, generating sparks as Rainbow's body came to a screeching halt. She flipped and did a somersault, landing onto her side and slamming her head against the hard rock floor with a grunt. She panted uncontrollably, her tongue suspended wearily from her mouth. "Vincent! Help..." Her pleas for help were feeble and muted. She splayed her limbs and attempted to lie as still as possible to recover from the exhausting sprint. Blood beaded and gradually trickled down the side of her head near her ear where shards of rock had pierced her skin. Her stitches had loosened and were poking into her skin.

Her opportunity to recover her energy wasn't prolonged. An invisible force commanded her body to rise. She was forced to grimly march forward, guided like a lifeless puppet suspended by strings. Terrified, her eyes darted across the room, searching for what or who had so effortlessly ensnared and dragged her body.

Subdued, blue-tinted light radiating from magical crystals suspended from the ceiling illuminated the innumerable skeletons blanketing the macabre chamber she now resided in. The blue light reflected off of the smooth white bones. Bones once belonging to creatures large and small. Horned skulls once belonging to unicorn ponies or creatures that once resembled unicorn ponies.

In the center of the mountain of corpses arose another stone altar. Beyond the intimidating altar was a gigantic creature suspended from the back wall of the chamber. It was undeniably a living creature, judging by how its form gently pulsated and quivered like a beating heart. The center of the creature was heart-shaped, while its long limbs—that which anchored it to the stone wall—resembled thick tree roots. It was covered in irregular, gnarled tree-root-like "skin". Tiny black antennae that resembled hairs protruding from the Heart jiggled as Rainbow's legs continued to unwillingly move, plodding her body forward toward the Heart.

She swallowed fearfully, her eyes darting between the corpses that lied at the very base of the altar. A small bipedal dragon. A werewolf-like creature. A pegasus-like juvenile bird of prey. More. Their bodies hadn't been bludgeoned, pierced or otherwise marred. They were perfectly preserved, as if they had all simultaneously fallen asleep and never woken up.

The Heart had no method of locomotion. It was purely a parasitic creature through and through. It drained creatures of their magic and abandoned their useless, lifeless bodies. Rainbow finally understood. It hadn't been a voice tempting her. It wasn't her destiny to discover the creature. She had stupidly fallen right into its trap, like a clueless fly in a spider's web.

"Dash?! I— Whoa... holy shit." Rainbow could hear Vincent's voice behind her, outside of her field of view. She wanted desperately to communicate in some way, or to bellow a yell of frustration, but she no longer had control of her mouth, tongue or throat. She could do nothing but continue to grimly march forward, unconsciously kicking aside the bones of the deceased. She was wholly paralyzed, imprisoned in her own body.

Desperate, she again attempted to establish a magical connection with her sapphire pendant, but to no avail. She could almost visualize her magical energy being drained from her body like sap being tapped from a sugar maple tree.

She was becoming lightheaded from oxygen deprivation. She was gradually fading, her perception of the world surrounding her slipping away. An oppressive darkness swirled around her, swooping in like hungry, eager vultures. Rainbow teetered over the edge and fell down into the dark, insatiable void, passing out entirely as her limp body collapsed onto the cold, uncaring stone ground and the bones of the tragically misled. Her assimilation was almost complete.