After recovering from the spell, Twilight looked around and saw she was in some sort of crystal cave.
"Hello?" Twilight called as her voice echoed, "Is anyone there?"
Twilight continues looking in the area around her until spots a familiar hedgehog lying on the ground unconscious.
"Sonic!" Twilight called as she ran towards him.
"Come on Sonic, get up!"
After shaking him for a bit, Sonic finally begins to stir while letting out a groan.
"Twilight?" Sonic groaned before looking around, "What happened?"
"Cadence trapped me in here," Twilight replied, "but what I want to know is what happened to you, why didn't you make it to the wedding rehearsal?"
"Well, it was after we said goodnight to each other, " Sonic explained, "I was on my way back to my room when I noticed a guard acting suspicious. I decided to follow him for a while and ended up outside Cadence's room. After he knocked on her door, I planned on spying on them but someone struck me in the back of my head. Everything was black after that."
Before anything else could be said, the duo hears a laugh echo around them.
"Welcome to the caves beneath canterlot, once home to greedy unicorns who wanted to claim the gems that could be found inside. And now, your prison." Said a voice that the two instantly recognized.
"Help, help!" Twilight called.
“It’s no use,” mocked Cadence. “No one can hear you, and no one will ever think to look for you either. Most ponies have forgotten that these caves even exist. Which is why they are a great place to put those who try to interfere with my plans.”
“Plans?” asked Twilight. “What plans?”
“The plans I have for your brother, of course.”
“If you lay one hoof on him...!” Twilight growled, eyes narrowed in fury.
“I’d love to see you try to stop me!” Cadence laughed wickedly, her horrid cackles vibrating throughout their gemmed surroundings, ringing in both Twilight and Sonic's ears.
"You won't get away with this!" Sonic called out.
"But I already have!" Cadence laughed.
Enraged, Twilight shots a bolt of magic while Sonic shots a chaos spear at the wall the reflection of Cadence was, causing it to shatter, and allowing them to see an unkempt Cadence.
Without a second thought, Twilight immediately charges towards her.
"No! Wait!" Cadence exclaimed before being tackled by Twilight, "Don't hurt me!"
"Twilight, it's me! You've got to believe me! I've been imprisoned like you. The Cadance who brought you down here was an imposter."
"Likely story." Twilight said sternly.
"Hold on Twilight, let her prove to us she's not an imposter herself." Sonic said.
Given a chance, Cadence begins to do the chant, "Sunshine, sunshine, ladybugs awake..."
Twilight then began to sing along, "Clap your hooves and do a little shake."
"You remember me!" Twilight exclaimed as she hugged Cadence.
"Of course I do. How could I forget the filly I love to sit for the most?" Cadence asked.
"It's good to see you for real this time cuz." Sonic said.
"It's good to see you too Sonic."
"Before we get too distracted on our little reunion, we still need to stop that imposter." Sonic said, "Come on, I actually know the way out of here!"
With that, the trio run off until they find a conveniently placed mining cart and hopped into it.
While they rode, Twilight spoke up, "Hey Sonic, you said something about recognizing this place earlier, how do you know about this place anyway?"
"Well it a few years ago back when I liked to mess around with the chaos emeralds," Sonic explained, "I was using chaos control to teleport myself to random locations until I wound up here. Being as curious and adventurous as I am, I definitely to explore the place for a bit since I can use chaos control if I can't get out on my own. I eventually found an exit and decided to come here every now and then to get some gems for Spike."
"Well, that explains where you got all those gems you would give Spike before we moved to ponyville." Twilight said.
Once the cart reached the end of the tracks, they spotted a light and immediately knew it was the exit. Before they could reach it however, there mares blocked their way.
"We don't have time for this." Sonic said.
"I'll handle it." Twilight said as her horn lit up.
Then seemingly out of nowhere, a bouquet enveloped in Twilight's magic appears and is shown to the mares, catching their attention.
"Fetch!" Twilight exclaimed as she threw the bouquet away.
"Mine!" The mares exclaimed as they chased after it.
"I know we're in a hurry and all, but that was way too easy." Sonic admitted.
"Let's just be glad it worked." Twilight said, "Now come on!"
With that the trio bolt out of the caves in hopes of stopping the wedding before it's too late.
In the chapel, It seemed as though time was almost up as Princess Celestia began to finish the vows.
"Where’s Twilight?” inquired Applejack in a hushed tone, somewhat worried about where her best friend could possibly be. “Ah hope she’s alright.”
“Surely she’ll be fine, darling,” reassured Rarity in a quiet voice.
“Princess Cadence and Shining Armor,” said the Princess, “It is my great honor to pronounce you-”
"Stop!" Twilight called as she and Sonic bursts through the chapels doors.
"We object!" Sonic said, causing everyone in the chapel to gasp.
“Uuugh,” groaned imposter Cadence angrily, “Why does she have to be so possessive of her brother?”
She then began to sob, “Why does she have to ruin my special day?”
“Because it’s not you’re special day,” announced Cadence, walking in the chapel. “It’s mine.”
This causes everyone to gasp again.
"What? But how did you get past my bridesmaids?" Imposter Cadence angrily asked.
"Nothing drives away bridesmaids better than a banquet." Sonic responded.
"Very clever, but it's still too late." Imposter Cadence said.
"I-I don't understand. How can there be two of 'em?" Applejack asked.
"She’s a changeling.” Cadence explained, pointing her hoof at her doppelganger on the altar. “She transforms into somepony you love and then feeds off your love for them!”
Just then, imposter Cadence is surrounded by a ring of green fire as she transformed into a changeling. She grew into a taller, black pony-like form. Her thin body was masked in thick armour of insectoid chitin. Her now longer legs were covered in holes like Swiss cheese. Her feathered wings became clear and insectoid as well. Her eyes became draconic and green. Fangs grew from her snout, and her mane became a seaweed green mess, topped of with a strange crown and a horrible crooked horn.
"Right you are, Princess. And as queen of the changelings, it is up to me to find food for my subjects. Equestria has more love than any place I've ever encountered. My fellow changelings will be able to devour so much of it that we will gain more power than we have ever dreamed of!" Chrysalis exclaimed.
"They'll never get the chance! Shining Armor's protection spell will keep them from ever even reaching us!" Cadence said back.
"Oh, I doubt that. Isn't that right, dear?" Chrysalis asked Shining Armor.
"Mm-hmm." Shining Armor replied.
Cadence began to make her way towards Chrysalis but it doesn't go unnoticed.
"Ah, ah, ah. Don't want to go back to the caves, now do you?" Chrysalis asked, "Ever since I took your place, I've been feeding off Shining Armor's love for you. Every moment he grows weaker and so does his spell. Even now, my minions are chipping away at it"
Outside the city it can be seen that a whole swarm of changlings are smashing into the barrier, causing it to crack every time they did so.
"He may not be my husband, but he is under my total control now." Laughed Chrysalis.
This causes Twilight and Cadence to gasp while Sonic stares at Chrysalis with anger.
"And I'm sorry to say, unable to perform his duties as captain of the royal guard." Chrysalis continued.
"Not my Shining Armor!" Cadence exclaimed.
"Soon, my changeling army will break through. First, we take Canterlot. And then, all of Equestria!" Chrysalis said before letting out a wicked laugh.
"No." Princess Celestia spoke up, "You won't. You may have made it impossible for Shining Armor to perform his spell, but now that you have so foolishly revealed your true self, I can protect my subjects from you!"
Princess Celestia then fires a golden beam of magic at Chrysalis, who fires a beam of her own to counter. To everypony surprise, Chrysalis' beam overpowers Princess Celestia's beam and sends her into the wall, scorching her horn in the process.
"MOM!" Sonic exclaimed as he rushed to Princess Celestia's side, soon to be joined by Twilight.
At that moment, the barrier around canterlot finally shatters and the changlings begin their attack.
"Ah! Shining Armor's love for you is even stronger than I thought! Consuming it has made me even more powerful than Celestia!" Chrysalis laughed.
"Mom! Are you okay!?" Sonic desperately asked, "Come on! Speak to me!"
"The Elements of Harmony. You must get to them and use their power to defeat the queen." Princess Celestia weakly said.
"She's right!" Sonic exclaimed, "Twilight! You and the girls get the Elements of Harmony, I'll deal with the queen."
"Right!" The mane six exclaimed before running off.
"You've got nerve hurting my mom like that while I'm around." Sonic said as he faced Chrysalis.
"Oh please, I'm not scared of you!" Chrysalis said.
"If I can deal with Nightmare Moon and Discord, I can deal with you!" Sonic exclaimed before charging at Chrysalis.
"Your cockiness will be the end of you!" Chrysalis exclaimed before firing a beam at Sonic, who side stepped to dodge it.
Once he was close enough, Sonic delivered a punch to Chrysalis' face, sending her into the wall. Chrysalis then shots bolt of magic in random directions in attempt to overpower Sonic, but the hedgehog was able to easily dodge them all.
Sonic then attempts to attack Chrysalis again but the changling queen was able to dodge his attacks and fires another beam that strikes Sonic in the back and forces him to the ground.
Sonic attempts to get back up, but is finding it difficult to do so due to all the pain.
"It looks like I've got the crown Prince of equestria on the ropes." Chrysalis said, "For so much talk, you can't seem to be a good fighter."
"Shut up." Sonic said as he raises himself onto his hands and knees.
"I was expecting something better from someone who defeated both Nightmare Moon and Discord, but they must have been incredibly weak for you to do that." Chrysalis continued as she made her ear towards Sonic.
"Shut up." Sonic said with great irritation.
"Now all you subjects will look down upon you for failure them." Chrysalis mocked as she stood before Sonic.
"Shut up!" Sonic yelled.
"You and your mother are weak! You both never stood a chance against me, and now I'll show you what happens when you mess with me, Chrysalis, the queen of the changlings!" Chrysalis exclaims as she raises her front hooves to stomp on Sonic.
When she drops them down however, Sonic catches them with one in each hand. Chrysalis then notices Sonic had a dark aura around himself.
"You think I'm weak, huh?" Sonic asked.
"Well, how about this!?!" Sonic exclaimed as he pushes Chrysalis off of himself, forcing here into the wall again.
When Chrysalis recoveres and turns to face Sonic, she finds Dark Sonic staring at her with a glare in his blank eyes.
"Sonic?" Princess Celestia said weakly.
"Save your strength mom," Dark Sonic said in his slightly deeper voice, "You deserve it."
"Amazing, even when you're full of rage, you still show love to your mother, now that is something I'd like to get my hooves on." Chrysalis said.
"I'd like to see you try." Dark Sonic said before seemingly vanishing into thin air.
"What the!?" Chrysalis exclaims before being his with a barrage of kicks, punches, and homing attacks.
"Having trouble keeping up?" Dark Sonic asked with a smirk.
Chrysalis answers by firing another beam are Dark Sonic. Said dark hedgehog shots a chaos spear to counter and watches as it slices through the beam and strikes Chrysalis and literally blowing up in her face.
Struggling to recover from the hit, Chrysalis realized she couldn't beat Dark Sonic in combat and decided to play dirty.
Without warning Chrysalis teleports in front of Princess Celestia and points her horn towards her.
"Don't move otherwise your mother gets it!" She warned.
"Don't stop Sonic, keep fighting!" Princess Celestia exclaimed.
"Keep quiet!" Chrysalis exclaimed as she moved her horn closer towards Princess Celestia's neck.
"Leave her alone!" Dark Sonic demanded.
"I will do no such thing." Chrysalis said before smugly saying, "Unless, you surrender."
"Coward!" Dark Sonic yelled.
"Well, what's your answer?" Chrysalis asked as she begins to charge her horn.
Dark Sonic angrily stares at her for a moment before dropping his arms to his sides, slumping his head, and turned back to his normal self.
"That's a good boy." Chrysalis laughed, "Changlings, seize him!"
With that several changlings appear and begin to close in on Sonic until they begin to block his view.
Later we can see Princess Celestia imprisoned in a cocoon made of green goo, Cadence's hooves are glued to the ground by the same substance, and Sonic is glued to the way by his arms and legs, his head still down.
"You won't get away with this! Twilight and her friends will–" Cadence began until the doors to the chapel open, revealing the mane six apprehended by the changlings.
"You were saying? You do realize the reception's been cancelled, don't you?" Chrysalis asked before ordering, "Now! Go! Feed!"
With that, the changlings leave to do just that.
"Speaking of feed." Chrysalis said before turning her attention towards Sonic, "You're just a ripe fruit that's just waiting to be picked."
Chrysalis then makes her way towards Sonic until she stood before him, and then began to move her horn towards his head.
"Unless you want to loose that horn, I wouldn't if I were you!" Sonic warned as a dark aura surrounded him once again.
"And just how would you do that?" Chrysalis smugly asked.
"I can free myself if I wanted to, but am deciding otherwise for my mother's sake." Sonic growled in response.
"Hmmm, I think I'll save you once I'm done with Shining Armor." Chrysalis said, "And you will be far more useful that he ever was!"
This caused Sonic to growl yet again and the wall behind him (specifically the areas behind his hands and feet) begin to crack a little.
Feeling sorry, Applejack decides to apologizes on behalf of everyone, "Sorry, Twilight. We should've listened to you."
"It's not your fault. She fooled everypony." Twilight assured, before realizing Chrysalis was putting all her attention towards Sonic. She then fired a beam at Cadence's hooves, allowing said mare to become free.
Once she was free, Cadence immediately ran towards Shining Armor and gave him hug, breaking him out of his trance.
Wha– where... huh? Is...is the wedding over?" Shining Armor moaned.
"It's all over!" Chrysalis exclaimed.
"Shining, your spell! Perform your spell!" Twilight called.
"What good would that do? My changelings already roam free." Chrysalis chuckled.
Shining Armor attempts to use his magic but finds that it's been drained
"No!" He exclaimed, "My power is useless now. I don't have the strength to repel them.
"My love will give you strength." Cadence said as she moved closer towards Shining Armor.
"What a lovely but absolutely ridiculous sentiment." Chrysalis chuckled.
Cadence then suddenly takes out a chaos emerald from under her wing and closes her eyes. After a moment, a pink aura surrounds her before she and Shining Armor connect their horns.
It's then a pink magic whirlwind begins to form around the couple as it begins to lift them in the air. After a few seconds, the couple open their eyes and releashed a pink shockwave that was unaffective on ponies, but it worked excellently on changling being how they were being pushed back by it.
"Nooo!" Chrysalis exclaimed as she and her changlings were scattered far away from equestria.
Once everything died down, Sonic uses chaos control to teleport himself to the cocoon Princess Celestia was still trapped in. Then then uses chaos spear to destroy the cocoon and quickly uses chaos control again to safely teleport the both of them to the ground.
"Is everyone alright?" He asked.
""Just fine." Twilight responded.
"Are you back to your senses Shining?"
"Don't worry Sonic, I'm fine." Shining Armor responded.
"Some day today was, am I right?" Sonic asked.
"You definitely got that right." Rainbow Dash said.
"If today was crazy I can only imagine how the rest of your guy's marriage will be like." Sonic joked, earning a laugh from everyone.
"Despite everything that's happened, I hope you learned a lesson on doubt, I know I have." Princess Celestia said before earning a few nods.
"Before we get distracted, how about we clean up for a bit and get this wedding rolling again?" Sonic suggested.
"Let's do it!" Everyone exclaimed.
A few hours later after the wedding, the Princess', the mane six, Shining Armor, Spike, and Sonic (who had his cape and crown on) were gathered in the throne room, discussing the days earlier events.
"I still say we were lucky when Twilight freed Cadence when she did." Rainbow Dash said.
"You got that right Rainbow Dash, but something is still bothering me." Twilight said.
"What is it Twilight?" Princess Celestia asked.
"Well what I want to know is, how did Cadence get one of the chaos emeralds?"
"Sonic gave it to me." said mare answered.
"But how is that possible?" Princess Celestia asked,"Sonic was near Chrysalis throughout the battle, he didn't go anywhere near you."
"Well it was after Sonic turned into that 'dark form'..." Cadence began to explain.
On the sideline of the battle, Cadence was unsure what to do.
"What should I do?" She asked herself, "Go to Aunt Celestia's aid or go to Shining Armor?"
"Cadence." Said a voice.
When Cadence turned she saw Dark Sonic standing in front of her.
"Sonic? But how?" Cadence asked as she saw Chrysalis fighting another Dark Sonic, "How are there two of you!?"
"I'm a clone, and I was told to give you this." Dark Sonic explained as he held out a chaos emerald.
"A chaos emerald? But Aunt Celestia told you not to let anyone come in contact with them." Cadence said.
"Unless it's an emergency." Dark Sonic said.
"But I can't take this!" Cadence exclaimed.
"Yes you can! I need you in case something goes wrong. I know you can do it Cadence." Dark Sonic assured.
After hesitating for a bit, Cadence takes the chaos emerald and tucks it under her wing.
"Thanks Cadence, I know I can count on -" Dark Sonic said before suddenly vanishing.
Before She could question what happened, Cadence finds herself surrounded by changlings before they began to close in on her.
"...And that's how I got the emerald." Cadence finished.
"Smart move Sonic." Rainbow Dash said
"I try." Sonic said.
"As grateful as I am, I'm still concerned about that 'dark form'" Princess Celestia said.
"I've been needing to talk to you about that." Sonic said, "You see, I lied when I said it was gone."
"What?" Princess Celestia asked.
"You see, I learned that the chaos emeralds are powered by one's emotions." Sonic explained, "Depending on how the user feels and desires, is the type of energy the emeralds make. A happy-going person with a pure heart will be able to use positive chaos energy. Someone full of hatred and with bad intentions however, they'll use negative chaos energy."
"What about you?" Twilight asked, "You don't have bad intentions."
"And that's why I was still in control." Sonic continued, "I'm too strong willed to lose myself in the negative energy. Although it takes practice, anyone with good intentions can use an type of chaos energy."
"But that still doesn't explain why you lied." Princess Celestia said.
Sonic sighed before saying, "I lied because I didn't want you to worry. If I told you the truth, you would of became overprotective and attempt to 'rid' the darkness out of me. But there's nothing you can do. It's a part of me now, but I can control it, so there's nothing to be worried about."
After thinking about it for a bit, Princess Celestia realizes she actually would of done all that if Sonic had told her the truth.
"You've right, my attempts to protect you would of blinded me from the truth." Princess Celestia said in a glum tone.
Not wanting to see his mother like that, Sonic walks up and hugs her.
"Don't worry mom, I wouldn't hold it against you. You're just trying to protect me is all." Sonic assured.
"Thank you Sonic." Princess Celestia said as she returned the embrace with her wings.
After they broke the embrace, Rainbow Dash asked, "So, how are you able to activate your dark form, Sonic?"
"Most likely if I become angry enough, but I think I can activate it without any anger but it'll probably be a while before I can do that." Sonic answered.
"Either way as long as you can control it I'm okay with it." Princess Celestia said, "Also thanks to all the information you gave me Sonic, I decided to allow you to let others use the chaos emeralds more freely but you still have to be careful."
"Don't worry mom, I will."
"Hey Sonic, do you think you can tell us about all the adventures you and the girls had so far?" Shining Armor asked.
"No problem." Sonic responded.
In the outskirts of canterlot, a purple mist appears out of the darkness until it takes shape of a pony.
"They will pay for what they have done!" The figure said, "Especially that hedgehog!"