Bones
Twilight awoke to the sound of moving sand.
Twilight tried to roll over, grumbling, but found her legs tangled up in something. Trying her best, she just couldn't seem to get it off her legs. It was really stuck on there, whatever it was.
Finally she opened her eyes and found that...
She had knotted the blanket around her legs in her sleep.
It was the work of a moment to unwrap herself. Now, legs finally free, she turned her head to the mouth of the cave to figure out what was making that digging sound. She found that the entire mouth of the cave was filled in with sand, the shield spell they used to keep the cave clear having collapsed sometime during the night.
Sticking out of the mound was the back of a changeling queen, digging sand by hoof. Twilight was about to go and see if she could help her out when her stomach grumbled at her. Twilight knew she couldn't actually open the saddlebag that held all her food, which annoyed her, but she knew very well the reasons for it.
"Umm. Naudia?" Twilight said, coming up beside her.
Naudia looked too preoccupied to hear Twilight, so she decided to playfully poke Naudia in the ribs to get her attention.
Naudia shrieked, bumped her head on the ceiling of the cave, and nearly started rolling down the massive pile of sand that was blocking the cave entrance.
Naudia picked herself up rubbing her head. "Oh..." Naudia looked nervous at seeing Twilight for just a second, then visibly tried to perk up. "Good morning Twilight!"
"Good morning! Umm, do you think I could have breakfast? I have an idea of how I could help you out with this sand."
A minute later, Twilight was sitting down to savor another meal of that truly amazing strawberry fungus. She noticed acutely that Naudia wasn't eating. Come to think of it, Twilight hadn't seen her eat ANYTHING since her disguise dropped.
"So, I haven't seen you eat anything for days now, aren't you hungry?"
"Didn't I already tell you?"
Twilight shook her head.
"I could have sworn that I did. Changelings eat emotions."
Twilight looked rather shifty at that.
"Well, yes, we can do it forcefully--as you no doubt suspect--or by impersonating somebody. Both methods have downsides."
"The forceful method will cause fatigue and headaches on the target. It’s unpleasant and easy to notice. It doesn't have any lasting effects. Impersonation used to be considered ideal, but you need to be able to impersonate somepony well enough not to be found out, and there are still some symptoms in the target, if you stick around them long enough."
"The last method, the one we avoid, is simply by trying to earn those emotions... as ourselves. It has no side effects, if successful, as love freely given can be freely taken. But it’s the most dangerous."
"Why is it the most dangerous? It doesn't sound nearly as dangerous as impersonating somepony."
"Twilight, what is the first thing you felt after you saw my mother's true form?"
"Well, I was shocked, of course."
"And after that?"
"It’s all a little hazy. Things moved so fast. But definitely anger."
"Any hate?"
"What?" Twilight was annoyed at being led on through this conversation.
"Hatred, Twilight. Hatred is the emotion we avoid feeding on at all costs, even unto starvation. Other negative emotions are avoided as well, but hatred..." Naudia shivered. "Hatred, once consumed, breeds hatred inside a changeling, until it begins to cannibalize its own emotions, feeding upon itself until finally..."
"Death?" Twilight asked, horror etching her words.
"Worse, Twilight. They become corrupt changelings: amorphous masses of hatred that live to destroy."
This all took a moment to sink in for Twilight.
"So changelings can't feel hatred?"
"No, we can't feed on hatred, or the emotions of other changelings."
"That still doesn't explain why you haven't eaten anything, though."
"Is that really so hard to work out, Twilight?" Naudia placed a hoof over her shoulder. "It turns out that a certain purple unicorn might have feelings for me."
Twilight was quiet for a moment.
"Did I say something wrong?" A hint of worry crept into Naudia's voice.
"No." Twilight shook her head, "It's nothing. Now, let’s deal with this sand, all right?"
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The Badlands, a seemingly endless rocky desert wasteland. It looked old and dead. From a geological standpoint, however, it was very young, and bristling with unique wildlife that fed off the vast reserves of expelled magic that, over time, had seeped into the desert like salt in the sea. Ancient magic, that was first released when the gods that fought in the Badlands were defeated, twisted and transformed the bodies of what survived there.
Small, spiky creatures that resembled a cross between fish bones and kites floated around one rocky outcropping in particular, which was radiating a much higher-than-normal background magic.
A sandy dune at the base of the outcropping exploded outwards in a hail of sand to reveal a cave cut into the rock itself, and a lavender unicorn stepped out.
"See? Much easier than digging, Naudia!"
The unicorn was followed by an agitated changeling queen attempting to walk and clutch her ears at the same time.
"You could have warned me first, Twilight."
"WHAT?" shouted Twilight.
"I said, you didn't conjure me any earplugs, Twilight."
"Why would you want ear bugs in the first place?"
Naudia sighed, and walked over to pop the faintly glowing earplugs out of Twilight’s ears so they could converse without shouting..
In the shadows of the rock, something oozed deeper into a crevice, so as not to be seen, before slithering off into the desert.
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As the miles passed under Twilight's hooves, she began to feel like she was getting the hang of this whole "adventuring across the desert" thing. Sure, the librarian wasn't in the best shape she could have been, but Twilight had found a rhythm that made the rolling dunes pass by almost unnoticed.
What she couldn't get around was her boredom. The rock-strewn desert was nothing much to look at, even at the best of times, and down in the valley between two sand dunes there was even less to see.
The only thing to look at was the skeletal, fish-like creatures circling high above. As Naudia told her, these “Mana vultures” fed on the energies left over after a spell was cast, as any spell left a sort of negative mana imprint equal to the mana used by the spell. These vultures cleaned that up, somehow, and used this negative mana to feed themselves. Apparently, there was enough spent mana out here for them to survive on that, although Naudia did say that the orbit of the sun and moon also left a similar imprint.
Twilight was so wrapped up in this that she almost didn't notice something go CRUNCH underneath her hoof. She looked down to find something poking out of the sand.
Naudia came back to find Twilight frozen in horror, staring at a bleached white skull poking out of the sands: A changeling skull.
There was a long moment of silence.
"Come on, Twilight. We need to get moving."
"But..." Twilight hadn't broken eye contact with the skull for several seconds.
"There is nothing we can do for him now, Twilight. We need to get moving." Naudia said again, patiently.
It took a while, but Naudia finally managed to get Twilight walking again. She still looked horrified.
"I don't know how he died." Naudia said abruptly.
"What?" Twilight said, caught off gaurd.
"There are too many things that could have happened to a changeling out here in the Badlands. Monsters, sandstorms... a war."
Twilight looked shocked. Equestria hadn't been in a war in what non-immortals would call “living memory.”
"The history of the Badlands is not a happy topic. Most of it was driven by desperation, but oftentimes, it was greed, or even petty-minded stubbornness."
Twilight still looked upset.
"Try not to dwell on the history of the Badlands too much. It is a cold and unpleasant place to be."
And they walked onwards. Twilight had lost her happy rhythm, and they trudged among the dead sands, that swept over the dunes and into the circle of sand around the fragile horned skull.