"So, where are you taking me?" Starlight Glimmer asked as her former teacher led her to a dark hallway in the castle.

Twilight Sparkle did not answer and instead gestured for Starlight to follow her.

The two mares, accompanied by Spike the Dragon, reached a small yet intimidating door. Glimmer tried to open it, only to discover that it was locked. She tried to teleport inside, but the room somehow sent her outside. She let a groan of frustration.

"That's not how it works. This place has only one way in and one way out. And only I can open it," Twilight explained. Her horn then activated, and a golden key with her cutie mark appeared out of thin air. She used to unlock the door.

The three of them went inside. It was dark. The alicorn used her magic to light the torches on the wall.

Starlight has seen dungeons before. And what she saw looked no different. There a big cell. There was little in terms of furniture; two beds, a book shelf and a crate. Curious, she walked towards the open cell and stepped in.

"I wouldn't stay there if I were you," Spike warned.

"Why?" the unicorn was busy examinng the cell to pay attention. She wondered why Twilight had brought her here. This was just an ordinary prison, right?

Before she could understand, Glimmer heard a noise and looked around to see Twilight locking the door.

"Ha, ha, very funny." Starlight tried to activate her horn.... only to find her magic gone. She was shocked, "What?!"

The princess smirked, "Spike warned you. This is no normal dungeon. This place is anti-magic. There's only one key, which appears out of thin air only me. When the door is locked, the magic and strength of anyone in is disabled. There is no escape."

Starlight was confused, "When did you discover that?"

______________________________________
Flashback prior to Season 5

Twilight roamed around the gigantic castle, followed by her number 1 assisstant, answering the same question for the fiftieth time.

"Spike, I'll tell you one last time. A self-tour of this place is nessecary. This castle appeared out of nowhere yesterday! Don't you wanna know what's in it?"

They arrived in front a dark hallway where they a small locked door. Sparkle tried using magic to get in but in vain.

"Um, do you have any idea how to get in?" Spike asked.

Twilight focused all her willpower on her magic, mumuring under her breath, "The key, please..."

Spike tapped her hoof, "Uh, Twilight, you should look."

A golden key with Twilight's cutie mark was lying on the floor. They got in.

A dungeon is what the pair saw. The mare entered unlocked the first cell and went in, leaving the key outside.

"Spike, lock the door, please."

No magic.

Spike unlocked the door, letting Twilight out. This wasn't the only cell as there were many others aligned, hidden out of sight.

Twilight tapped Spike's claw, "I think we should keep this a secret."

"Definitely."

End of Flashback
________________________________

"Okay, so that happened. But why did you bring me here?" Starlight was still confused.

"I thought you could the perfect test subject to confirm my theory," Twilight smiled.

"What theory?"

"The cell takes your magic to strengthen itself and make your escape more impossible," Twilight explained.

"Ooookay. What's this?" Starlight pointed to a small rectangular hole in the bars.

"That's my cue," Spike rushed upstairs and came back two minutes after with a rectangular food tray that fit the hole perfectly.

"It looks like the tree thought of everything. Even food," Twilight laughed. Spike went back.

"Sooo, is this place still a secret?" Starlight inquired.

"That's correct."

"And has it never occurred to you that you make it be known to the public? This dungeon could be really useful to hold dangerous criminals and such things," Starlight suggested.

Twilight considered it, "Right. I'll make the princresses know." And with that Twilight dashed out of the dungeon, leaving behind poor Starlight who was still locked in the cell.

"No, wait! Twilight! You have to let me out! I don't know for how long you'll be out! I don't wanna stay here! TWILIGHT!"

Author's Note

So, there goes my very first fanfic. Its also my personal headcanon. Hope you enjoyed it. Comment your thoughts below, please! Let me know if there typos. Any other tags I should I should add?

On a side note, I have no idea how to introduce a flashback. Any suggestions?

Also, the dungeon will appear in many of my stories. It will referred to as 'Twilight's Dungeon'.