After departing from Gallop Cove, Sonic, Tails, The girls, and Spike were airborne again, pinpointing the next location.
"Alright Tails! Where to next?" Sonic asked, turning to face the young pilot.
Tails looked to his handheld which he had hooked up to the plane. "Hm…I'm getting some strange readings from a place called Canterlot. And by strange, I mean it's not just the next Element of Harmony." he said, looking to the blue hedgehog before glancing back down to the handheld. "Whoa! The readings are getting stronger! No wait...They're fading? Hold on. They're rising! Wait...I think something's interfering with the signal."
Twilight used her magic to teleport behind Tails before grabbing onto the seat to avoid falling. "Let me see! I have some experience in reading energy levels so maybe I could try and figure this out." she said before levitating the handheld to her face and examining the contents on screen. "Hmm...Ok I see Rarity's Element of Generosity...no wait scratch that. I see...2 of them? No 5? 1?! Ok something is definitely wrong here! We need to get to Canterlot as soon as possible!" she announced before levitating the handheld back over to Tails and teleporting back into the basket.
Sonic frowned. "That can't be good! Well let's head to Canterlot then!" he said.
Tails nodded before steering the plane towards Canterlot with the girls following close behind.
Once on the ground, Sonic jumped off the roof and turned back towards his sidekick. "Alright Tails. Where's the next energy signal?" he asked.
Tails turned the engine off and flew out of cockpit seat with his handheld in hand. "Over there! Right by that huge castle! Wait a minute...OH NO!" he exclaimed upon noticing Eggman's huge ship approaching in the distance.
Twilight looked in the direction of the fox's finger and went wide-eyed. "That's Princess Celestia's castle! And Eggman's heading right for it!" she panicked.
"No sweat! I'll beat him to it!" Sonic exclaimed before dashing off.
Tails and the others gave chase.
(Stage: Canterlot)
Sonic ran full speed through the bustling streets, quick-stepping many ponies to avoid slowing down. "S'cuse me! C'mon through! Watch it!" he warned as he ran by many ponies, mostly consisting of unicorns.
Twilight and the girls were right behind Sonic with the use of the purple unicorn's superspeed spell.
"We're right behind you, sugarcube! Uh oh! Clocktower incoming!" Applejack exclaimed before the girls screeched to a halt.
Sonic just kept going, running up the 90∘ angle
The girls watched in amazement as the blue blur reached the very top of the tower.
Tails joined Sonic at the top then noticed Princess Celestia's castle in the distance. "Look! There's the castle! And there's Eggman!" he said.
Sonic frowned, having no time to lose. "Time to speed up!" he exclaimed before jumping onto a rail that seemed to spiral around the tower. Sonic grinded all the way back down before boosting the remainder of the way.
Meanwhile at the castle, Princess Celestia was on her balcony, overlooking her glorious kingdom in worry, having just gotten word about an unknown enemy apparently planning an attack. One of her guards entered the room and bowed.
"Your highness, We still have no information regarding the whereabouts of Princess Luna. The guards have done a thorough search of the nearby area and found no signs of her." he explained.
Princess Celestia sighed. "Keep searching. Get help from any passers by if necessary. We will not stop until my sister is found." she announced.
The guard nodded. "Yes your highness." he said before walking out of the room, leaving Princess Celestia alone.
She turned back to her kingdom and noticed that the sun was beginning to set and the moon beginning to rise over the sky. The Princess grimaced. "It can't be...Nightmare Moon...has returned?" she stared in shock as Eggman's giant ship approached the balcony and stopped just centimeters away.
"A pleasure to meet you at last, Princess of Equestria!" Eggman greeted as his mobile hovered over with Orbot riding along inside. "I am Doctor Eggman. I come from another dimension with a deal for you." he said.
Princess Celestia frowned. "So you're the one that's been causing havoc for all my loyal subjects?" she asked.
Eggman chuckled. "Whatever do you mean Princess? I simply come with promises of a new and improved Equestria. All you need to do is surrender your kingdom to the Eggman Empire and I'll make the lives of your subjects a whole lot easier and happier! And you will agree to my plans Princess, one way or another!" he threatened. Suddenly, Buzz Bombers, Bat Brains, and Egg Pawns all had their weapons aimed at the ruler of Equestria!
Princess Celestia glared. "Never! I've vowed to protect my kingdom and its subjects from any harm. And I'm going to do just that!" she charged up her magic and aimed at Eggman before noticing a purple cloud appear in front of him and materialized into Nightmare Moon.
"Looking for somepony, sister?" she taunted.
Celestia gasped and ceased charging.
Eggman laughed. "Your sister is on my side now! So Princess, what shall it be? Will you surrender? Or shall I take this kingdom by force?" he asked.
"I…" she was about to answer before a series of explosions stopped her.
One by one, the badniks were engulfed by a fiery blast before Sonic had appeared right in front of the Princess. "My! That's a pretty snazzy performance there!" he exclaimed before finishing off the remaining robots.
Eggman growled. "You've done it now you repulsive little rodent! Nightmare Moon, destroy him!" he ordered.
Nightmare grinned. "With pleasure Doctor!" she said before turning back into a cloud of smoke and pursued the blue hedgehog.
(Boss: Nightmare Moon)
At the castle's entrance, Sonic had made a perfect landing and was about to go back but was stopped by Nightmare.
"Not so fast, hedgehog! You will have to wait until the doctor is done...unless of course you want to get through me!" she said.
Sonic grinned. "Nightmare Moon I presume? Well somepony's gonna be out like a light all right!"
Nightmare chuckled. "Do you know who I REALLY am? I am the TRUE princess of Equestria and soon, your demise! HAHAHAHAHA!" she laughed before taking flight.
Sonic dashed after her.
Nightmare attacked first by summoning thunderclouds to strike down Sonic but the blue hedgehog evaded them with no problem.
Sonic quickly jumped in the air before launching a Homing Attack on Nightmare. Just when he was about to hit, the mare in the moon transformed into the smoke cloud, allowing Sonic to torpedo right through her!
"What the?!" Sonic broke out of his spiky ball form and looked back towards Nightmare, surprised.
The mare laughed. "You may be fast, but not fast enough to strike me down! Now face my nightmare!" she exclaimed before using her magic to divert meteors from space and send them plummeting towards Sonic!
Sonic quickly reacted and homing attacked the space debris before trying to strike Nightmare Moon once again. Like before, the Homing Attack shot right through her! "Dang it!"
Nightmare cackled. "Did you honestly think you could defeat me you little fool! Nopony shall stop me this time! The night will last FOREVER!" she yelled before firing a series of laser shots from her horn.
Sonic dodged them as his mind began to race. 'C'mon Sonic! Think! How can you possibly hit her?!' He suddenly had an idea. Focusing his mind, he called upon the power of the elements and started drawing power from one of them.
LASER!
Sonic's body instantly transformed into a living laser beam of magic before zipping at Nightmare Moon and making direct contact, temporality stunning her. Sonic's elemental power wore off as he saw his chance to strike. "Here goes!" just as Nightmare Moon snapped out of her state, Sonic unleashed a chain of Homing Attacks, sending her to the ground.
"GRAHH! S-so...you managed to land a hit on me! But that won't do you any good! I've still got enough energy to take you out!" she growled before redirecting more meteors at Sonic, this time enveloping them with a dark wave of energy.
Sonic evaded them with ease before unleashing another homing attack on the mare, this time actually hitting her.
Nightmare Moon was growing furious. "Grrrr! You're getting on my nerves you little fool!" she growled before charging up her magic once again, this time releasing it in the form of a massive beam of energy! Sonic was hit and tripped but resumed running after Nightmare and dealing another blow to the mare.
"I'm done with you Sonic! Prepare for your end!" she screamed before landing on the ground and charging up her magic one last time.
Sonic didn't stop running and was pushed back by Nightmare's magic blast but began to boost through it. Nightmare summoned all her strength but the blue hedgehog slowly came closer and closer until he plowed right through her!
"NO!" she yelled. After going airborne, she regained control. "Y-You haven't seen the last of me hedgehog! The night will last forever!" she said before changing back into a cloud of smoke and flying back towards Eggman.
Sonic frowned and followed, hoping there was still enough time to save Princess Celestia.