The Curse of the Lost Prince

Twilight don´t know what to do now. She´s completely confused and has a lot in mind. Ever since Astral disappeared, everything has been a big mess. Everypony is in panic and asks a lot of questions that she can´t answer. Celestia and Luna had already gone to hold a "meeting", and Discord was with them.
But the worst thing about it is that Sweetheart is gone. It was 3 days ago, since the black pegasus took Astral and she don´t know where she was. Or, perhaps, maybe where she may be, but she has already checked their hideaway, but no traces of her.
She decides to take a trip to Canterlot's Palace Hall to think carefully about the situation. She thinks a lot about Astral and the mysterious pony that appeared in her party. And the most important of all; What is Astral trying to hide?
As she walked, she discovered Sweetheart standing in the middle of the hall. She called her, but suddenly she stopped. She tried to catch her, but she was really quick to run.
But luckily, Rainbow Dash came by and grabbed Sweetheart. "I got her!" she shouted to Twilight. Suddenly her friends already appeared, who already found Sweetheart, but was really hard to catch her. She found a room, so they can speak privately. Rainbow Dash put Sweetheart on the floor and they were all in the circle.
Twilight tried to talk with Sweetheart quietly until Rainbow Dash pushes her aside and demands to know what she has done to Astral. Sweetheart got really frightened, and Applejack pulled her tail from Sweetheart.
"There is no use to scare her. We must talk with her with patience," said Applejack with hr serious country accent. She smiled at Sweetheart and then lets Twilight take control.
She looked at her with a worried face, but she wasn´t angry. "Sweetheart... Please, for Celestia´s sake. Please tell us what's going on?" Twilight asks directly, but Sweetheart was just sitting there and shivering. Twilight waited patiently for her and even asks her more. "I... I can´t..." she whimpered. She was scared, she know that, but Twilight had to know if she can help her and Astral.
But Sweetheart still wounldn´t talk and Twilight was just about to lose her patience, but keeps her coldness. Fluttershy offered to try, which Twilight gave her permission to. She spoke to her with a calm tone as if they were whispering and it took not long enough as Twilight thought.
Fluttershy tells her that she has talked to Sweetheart. Twilight was waiting for the answer, but unfortunately Fluttershy said the same reply from Sweetheart, which was a disappointment. Rainbow means that it was waste of time and suggests why they just can´t seaching Astral for themselves. But Rarity and Applejack shushed at her and lets Fluttershy finishs her sentence. "But she knows where he is," Fluttershy concludes, who gave Twilight some hope. But she cannot stand it and would really like to know where he is. Sweetheart got frightend by her reaction, and Twilight was sorry about that. But she really need to know why she can't tell where he is. Sweetheart hesitated, but mumbled that she wasn't allowed to speak.
"But why? What prevents you not telling us?!" Twilight begged desperately. Sweetheart stared at the floor for a moment, but looks up and stares straight at her. "I can't, because... because..."

"Because she doesn't have my permission to speak!"

Suddenly the mysterious mare appeared like a whirlwind and frightened them all. She landed carefully next to Sweetheart, who looked so scared. But she smiled harmly at her. "Where's Astral?" Twilight requires demandly at the pegasus. The pegasus raised an eyebrow as if she didn't know any Astral. "...Astral... Oh, the Astral. I'm sorry to disappoint you, but he only used that name, when he's outside of my castle."
Twilight has already figured it out and didn't care what he was called in real life. For her, he's still Astral. But she even asked questionly to the pegasus, why Sweetheart cannot speak without her permission. The pegasus gives her a smirk and went to Sweetheart with her long legs and elegant steps. She even asked her if she have something to show to her "new" friends. Twilight took a glimpse at Sweetheart, but she hesitated. The pegasus stretched her wing towards Sweetheart, taking her mane aside where it revealed a mark. "As you can see, she´s bounded to me. AND she can´t tell you where your little friend is."
They were in shock. Especially Twilight. Now she better understood why Sweetheart doesn´t talk so much about him. But that doesn´t prevent her from giving up so easily. "What have you done to him ?!" she asked immediately. The pegasus mimicked her voice in a pitch annoying way, yet was disgusted by Twilight´s need for answer and friendship.

"If you really want to know, where your precious friend is, he's already home where he belongs. And there's nothing you can do about it!" she said with an evil smirk.

Twilight thinks it's not fair. But the pegasus mocks them by telling them that they´ll never find him without Sweetheart's help.
Twilight looked at Sweetheart with a sad expression. The pegasus has a point. Sweetheart can´t help her, if she´s under in sort kind of a curse. She looked at her friends completely clueless. Until she got an idea and said something clever to the evil witch. "If we can´t have help, why don´t you just let us find him?".
Sweetheart and her friends seems shocking what she said. But the pegasus just laughed like everything, she says was a joke. She asked her how in the whole world she should do it. Then Applejack came in - which she already figured out what Twilight was trying to do. "Yeah, if you're so sure about it. Then you have nothing to be afraid of."
The pegasus looked convinced and impressed by Applejack´s speech. She thought about it and decided to make an exception. She then explained, they´ll get a riddle about which way they should go. Sweetheart can help them, but she mustn´t mention or show the way. She means that would be cheating.
"If you wins, I´ll let your little friend go." she agreed to them for playing fair and square. "...If not, he belongs to me and I´ll make sure that you´ll never EVER wanted to remember him!"
Twilight's heartbeat stopped. Forget about Astral. That could be the doom, if she don´t beat the witch´s game. But Twilight proves bravely and says it's a deal. "I´ll make sure we wins this game. And freed Astral from your tyranny!" she said with confident. But the evil with chuckled and stares at her with viciously eyes. "I wouldn´t be so sure about that..."

Meanwhile later...

Twilight packed her stuff to her new quest. She packed a few books to read, ususally she would pack a mountain of books, but this time she only packed a book with blank pages. She´ll use it to write the riddles on her journey. She´s now ready. Her friends was waiting for her at the ruin. She said goodbye to Spike, which he promised her to look over the library, when she´s gone. It made Twilight a bit happy, where she gave him a warm hug and went from Canterlot.
Then, she met Celestia at Canterlot´s exit. Her eyes and face were sad and stared directly at Twilight. "You knew about him..." Twilight mumbled quietly. Celestia nodded, but Twilight don´t want an explaination and already understood why she kept it secret.
But before she could go, Celestia grabs her with her wing and looked at her. "Please... save him." she whimpered in tears. Twilight watched her crying like never before(besides Luna´s return). She stared confidently at her mentor and responded that she will save him. Whatever it takes in her new adventure...