One dark and rainy night, in the middle of the desert of Southern Equestria, a figure (anthropomorphic) in a black cloak with a hood wandered the sands. It was Nightmare Moon; not only had she managed to return, but now existed outside of her host, Princess Luna, albeit weakened, as she never had her own physical form. Hoping to regain her strength and plot her revenge, Nightmare Moon had placed herself in self-imposed exile until her power had full restored. This led to her being in the desert, hoping to seek shelter as she then saw something out of the ordinary. A cave entrance, with its passageway shown by rather ghastly white lights.

The moment when she came close enough towards one, the light disappeared.

Nightmare Moon:"Strange. It appears to be some unfamiliar source of magic. It does not seem like a good idea to move forward into the cave, but I do not have many options."

Heading inside as the lights disappeared around her, she used her horn as a lantern to light the way. There appeared to be nothing inside and no one around, except for a tunnel that just seems to go on.

Nightmare Moon:"Wherever this cavern leads, it's better than being out in the open."

For what felt like hours, she traveled into the cave. That is until she reached a black sandstone and a light blue floor, and in the distance she saw a bluish light.

Nightmare Moon:"What is this place?"

Reaching the end of the corridor, she stumbled upon an empty room with torches burning with a blue flame. As soon as she, without suspecting it, stood in a black circle, that lit up and deprived her of magic except immortality.

Nightmare Moon:"No! My magic..."

As soon as this happened, the passage behind her closed, but a new passage opened in front of her, consecrated by the same torches.

Nightmare Moon:"(sighs) So this is the point of no return."

Having reached the end of the next corridor, she stumbled upon a large gray hall, divided into 2 floors down by a balcony on which she stood and lit by torches with white flames. And in front of her, she noticed a corridor with white sandstones and an orange floor, and consecrated with ordinary torches. From this corridor someone in a white hooded coat comes out, and this gives Nightmare Moon sudden hostility.

Nightmare Moon:"No further, you. Are you the one who has trapped us here?"

Taking off the cloak, the figure was revealed to be none-other than her sister, Daybreaker.

Nightmare Moon:"What? Sister? What are you doing here?"

Daybreaker:"I can ask you the same, Sister."

Nightmare Moon:"I was in self-imposed exile until I could regain my strength."

Daybreaker:"I, as well. Though, while I was hoping for some sort of knowledge or power from this temple, it seems that we've both been led into a trap."

Nightmare Moon:"(sarcastically) You think?"

Cold Female Voice:"Daybreaker is correct. In fact, this entire place was made...just to ensure the two of you may never leave."

The two of them turn to see coming towards them an anthro demoness-jackal, and according to royal clothes, it was clearly some kind of queen. And suddenly jackal demons appear behind them and grab them, being servants to the jackal.

Nightmare Moon:"What is this?!"

Daybreaker:"You're making a big mistake. We are two of the most powerful beings in this world."

Jackal:"...Were. You were, my Daybreaker and Nightmare Moon. Allow me to introduce myself; I am Dimitra, the Jackal Queen, and we've been waiting a long time to return."

Nightmare Moon:"We've never even heard of you. What are you planning to do?"

Dimitra:"This place was built centuries ago, should a great evil ever return, we could imprison it here indefinitely. We are 4500 meters below the surface, and there is no magic for you to use here. And now, with all that aside, we can get you ready for your final resting place."

The jackal demons subduing the two had then placed rags soaked in sleeping potion over their mouths. Though they tried to resist, it was all in vain as the sisters quickly fell asleep. Dimitra enjoyed their slumbering forms as she then had her servants carry them up to the second floor, where they were to be prepared for their eternal rest.

There, they put them on tables, and began to undress them. Armor, clothing, even underwear, the sisters were laid bare as their clothing was placed and locked in chests. After that, they were taken into the next chamber for Dimitra's favorite part of burial, mummification.

A group of embalmers put rings on their horns to their foreheads that were magic inhibitors as an additional precaution, should their magic ever return. Then, splitting into two groups, one group takes black bandages for Nightmare Moon, and the other group takes white bandages for Daybreaker. They tightly wrapped their fingers and toes separately, then their limbs, tails and wings separately, keeping the winds folded and unusable. After wrapping their torsos tightly around their necks, they took needles with light blue thread for Nightmare Moon, and orange thread for Daybreaker, and sewed the bandages together tightly. Then they tightly wrapped their fingers and toes together and sewed the bandages together.

They pressed their legs and tail together, and tightly wrapped them together and sewed the bandages together. Crossed their arms over their chests, pressed their wings to their backs, and wrapped them tightly together, then sewed them together. They put ear plugs into the ears of the two sisters, and stuffed rolls of thick cloth into their mouths, after which they tightly wrapped their heads and horns, and tightly but carefully sewed the bandages together. After that, they took light blue ribbons for Nightmare Moon and orange ribbons for Daybreaker, and tightly wrapped their stitched-mummified bodies in lines and crosses, and sewed them to the mummified bodies.

They took long rolls of cloth: Light blue and orange, and then wrapped their mummified bodies tightly around them, sewed the edges of the cloth together, they took black and white ribbons, and also wrapped them in lines and crosses, and sewed them to the cloths.

Layer by layer, Dimitra enjoyed the two sisters being encased, to ensure it'd almost be impossible for them to escape.

They then took a black shroud for Nightmare Moon and a white shroud for Daybreaker, tightly covering their bodies, sewing up the holes behind them. Then they take light blue and sky blue ribbons for Nightmare Moon, and orange and hot yellow ribbons for Daybreaker, and they wrap their bodies tightly in lines and crosses, then sew them tightly to the shrouds. They then dressed them in ceremonial burial clothes, including burial masks with sleeping expressions; the horns of these masks had ring-like magic inhibitors as another extra precaution.

After the mummification was completed, they lifted and carried them to the sarcophagi specially prepared for them, and as soon as they put them inside, they tied them tightly with straps from the interiors.

Nightmare Moon and Daybreaker began to wake up, but it was already too late, as the jackal demons closed them inside with lids of sarcophagi with the same sleeping expressions. They could not even struggle underneath every layer they were mummified as their fates were sealed, figuratively and literally.

They locked their sarcophagi with special keys, then wrapped the black cloth tightly around Nightmare Moon's sarcophagus, and tied it with sky blue ribbons and sewed them to the cloth, then tied it tightly with light-peel ropes, and applied adhesive to the knots of the ropes. And at the same time, they did the same to Daybreaker's sarcophagus, only with white cloth, hot yellow ribbons, and orange ropes. Then they placed them in wrapped-tied sarcophagi in additional coffins, locked them with other special keys, and did the same as with the sarcophagi. They pick up wrapped-tied coffins and carry them to the central corridor of the second floor, to the burial chamber. Having reached there, they placed them in burial boxes, and locked them with special keys, after which they left the burial chamber and walled it up, then the central corridor too.

After that, the queen and her servants leave the tomb, and the servants wall up the entrances, and as soon as the queen left one of the two caves, both caves and tunnels were dug up and walled up by her servants as if these caves never existed.

Dimitra:"Sleep now, sisters, and forget forever. Eventually, you may be let out again."

Servant:"Milady, was all that really necessary. Not that it wasn't enjoyable, but you really think it's enough for the two sisters to change for the better?"

Dimitra:"Should they never escape, we will have to leave it to the ancient ones to sort them out. Otherwise, they will be at the mercy of the pink star. For she is the one with the knowledge to free them."

And with that, they disappear without a trace.