A strange sound filled the air of Ponyville, echoing in the ears of the residences. Looking up, they tried to figure out what it was, and where it had come from. Most that had heard it would have described it as a massive belch. The problem with that was that -- as far as most knew -- there was only one pony in Ponyville that could have performed such a feat, but she would have been at work. Plus, the ones that were at Sugarcube Corner knew it did not come from there. Pinkie Pie was behind the counter and was staring up just as much as the others.

Back at Twilight Sparkle's crystal castle, Twilight Sparkle and Spike stared at Nightmare Moon.

"Wow," Spike said. "I didn't think anypony but Pinkie Pie could eat that many pancakes. Or belch that loud."

For her part, Nightmare Moon was sprawled out, patting her swollen stomach. She had no idea that eating could be so pleasurable. It was something she would certainly have to experience again.

She would have to it experience again. She was mortal now, and mortal ponies needed to eat to live. Just like they needed to sleep. So long as she was trapped in this vessel, she would be forced to do the same.

Speaking of...

"Sparkle," she stated as she moved to sit up, "it seems that you have created a flawed vessel for my manifestation."

"I already told you," Twilight said in a calm but firm tone, "we couldn't make you a alicorn because it would be too dangerous."

"Not that," Nightmare Moon interjected (although she still was not happy about that and would get them all back for it later). "There are physical defects, which have caused complications this morning. For one, there was extreme discomfort -- bordering on painful -- in my abdominal section."

"Really?" Twilight asked, ears perked and eyes wide. "Do you still feel it?"

"...no..." Nightmare said slowly as she realized that she in fact did not. She looked down toward her midsection. The discomfort had vanished some time while she had been busy consuming pancakes. Now Nightmare Moon felt a sense of satisfaction, and that some of the muscles in her abdomen were being stretched.

"Well, hopefully it was just hunger pangs," Twilight said.

"Hunger pangs?" Nightmare Moon repeated. "You mean to tell me that if I don't eat for long enough, my body will actually make me uncomfortable until I do?"

"Basically," Twilight answered. "Most don't experience since they eat when they first feel hungry." She paused, tapping her chin. "Although, most have also been eating since they were born and are aware of when they are hungry. You, however, have probably never felt the desire to eat directly. Plus, you didn't eat anything at all yesterday." She turned to look back at the plate that had held the pancakes earlier. "Technically, this would have been your first meal ever.

"Hope it doesn't give you indigestion."

"Indigestion" was not a word that Nightmare Moon was familiar with. She would have to look it up another time to find out what it meant. It was not important at the moment.

"That eliminates one issue, but there is still another. The muscles of my limbs are resistant. When I awoke and tried to get up, they felt hard and unwilling to move. It made it difficult for me to rise. They also feel as though I am tensing them when I am not."

"Hard?" Twilight asked. "Tense? Would you be willing to call them 'stiff?'"

Nightmare Moon considered it a moment, considering the word and how it compared to her limbs earlier.

"Yes," she responded. "I suppose that would be an accurate description of how they felt."

"That is probably normal as well," Twilight stated. "When muscles are overworked, either from extensive use or singular excessive exertion, they can become stiff. In your case, they didn't exist before yesterday, and as such have not been used at all. All the walking from the cavern, through Canterlot, to the train, and then from the station to the castle was probably more exercise than your body is used to... seeing as you have never needed to any before... Or you did, but the body was already adjusted to it from natural growth..."

Standing there, Nightmare Moon stared at Twilight Sparkle, head tilted and one eyebrow raised. One of her ears gave a flicker as she processed what she had been told, and what it could possibly mean.

"So, you're claiming that this 'stiffness' in my limbs is a natural thing that most ponies go through?"

"Yes," Twilight replied, getting a snarl in response.

"If I over exert myself," Nightmare Moon growled, "I will suffer. If I don't eat, I will suffer. More than likely there will be other issues that will cause problems that I have yet to learn about."

"Well..." Twilight started, but was cut off by a hoof.

"No," Nightmare Moon stated. "Don't tell me. I think I have had enough worries placed on me this morning as it is." She let out a huff. "Unfortunate. I had been hoping that the issue could be resolved if this vessel were destroyed and I was given a new one."

There was a flicker of wings, drawing Nightmare Moon's attention. Twilight Sparkle's wings were spread wide as she stared, wide eyed and mouth hanging open.

"You..." Twilight started, her voice cracking. "You were going to ask me to murder you?"

"Murder?' Nightmare Moon let out a chuckle, giving a shake of head. "Dear silly little Sparkle, 'murder' would indicate that I was a mortal pony that was killed with no way of being brought back. I am a spirit that has been bound into an artificially constructed mortal body. If it were to be destroyed, it would merely mean that you would perform the ritual again to force me to be incarnated once more."

It was the fact that she could be incarnated again that had kept her from attempting to destroy herself. While on the train, she had considered if she jumped, it would most likely cause sufficient damage to make the body fail, releasing her. The main reason that she had not actually gone through with it was the fact that she would only be incarnated once again before she had been able to regain her strength. They might also place her in a weaker vessel, such as turning her into a filly. Being turned into a pony with almost no power was bad enough, being turned into a child with the mind of an adult would have been infuriating. Especially since she would have to learn how to manipulate adult ponies through the power of cuteness as opposed to fear and intimidation.

"Actually... it may not be that simple," Twilight said. "The spells and ritual we used were extremely old and mostly theoretical, although a few of them had included experimentation on a smaller scale. One of the ponies who was closest to actually trying on a full scale never did so. He... uhm... well..."

Throwing her head back, Nightmare Moon let out a growl of frustration.

"Really," she huffed at Twilight. "Must you take so long to speak? Get to the point already."

"You might actually be mortal and able to die," Twilight Sparkle blurted out.

Nightmare Moon could feel the muscles tense in her back as her eyes went wide, staring at Twilight.

"I must have misheard you, Sparkle. Perhaps you would care to repeat what you just said."

Twilight Sparkle's body sagged as she let out a sigh. Her ears pulled back as her wings flopped, head and tail drooping. Taking a deep breath, she straightened back up and looked at Nightmare Moon. There was something in Twilight's eyes that made Nightmare uncomfortable. Sadness? Regret? Pity? Nightmare Moon was uncertain what it was, but she did not like it directed at her.

"You didn't mishear me," Twilight stated. "The one pony that got closest to full scale experimentation never did. For some reason, he decided it would be a bad idea. The specifics of the thinking behind the process are unclear, but somehow he concluded that if a spirit were to somehow be manifested into a physical vessel -- such as a pony -- then they essentially become mortal. As such, if the vessel is destroyed, instead of returning to their realm, the spirit instead goes through the same thing as any other pony does after death. Basically, by becoming a vessel, the energy that was your spirit is your soul. If he's right, then when you die, you can't come back any more than a regular pony."

Nightmare Moon's eyebrows furled as she stared at Twilight. Her mind was running through what she had just heard, trying to process it.

"So you mean to tell me," she said slowly, "that -- according to whomever had been conducting such experiments -- not only am I stuck in a mortal body with almost no power, but I can now actually die like a mortal pony?"

"Yes," Twilight answered, crouching down and in on herself more.

"And what, pray tell, happens to a pony when it dies?"

"Well..." Twilight started as she considered the question. "Most believe that when a pony dies, their soul passes through a place where all its memories and experiences are saved. There, an incredibly few creatures that can find their way to that realm can access it. After, the soul is returned to the source of all life magic, where it mixes with others before being reborn as a new soul in another living creature."

"So not only can I die," Nightmare growled, "but if I do, I will be erased and born as another pony?"

"Not necessarily a pony," Twilight corrected. "You could just as easily be a griffon, minotaur, zebra, or any other sapient race on the planet."

"Gah!" Nightmare Moon roared out. "Enough! This entire thing is preposterous! If I didn't know better, I would think you were making the whole thing up to merely discourage my intentional destruction of this body."

With a final snort, she got up and turned around, heading for the doorway.

"Nightm-" Twilight started before being cut off.

"No! I have had enough for this morning. Whatever other terrifying news you have for this whole situation can wait."

"Actually," Twilight called out, "I was going to tell you that we are going to start off with a tour of Ponyville to help you learn your way around. I understand it's a lot to deal with, but we still need to work on your rehabilitation. So, you have half an hour to get ready before we head out for the day."

"I hate you," Nightmare Moon growled as she continued out the kitchen and toward the stairs.