For any mere mortal, the journey from Tartarus to the mainland of Equestria would be a daunting task which would take several exhausting days to complete, but the denizens of Tartarus were relentless; they marched hard with unwavering strength through forests, marshes and swamps, over mountains and teaming rivers until their goal was in sight.
As evening fell, Princess Celestia and Princess Luna - both fitted with iron battle armour - stood atop the lookout of their castle waiting for the oncoming forces. Beside them stood the golden Equestrian war horn which was so large it towered above the sisters' heads. Celestia peered through her telescope as Luna stood by the war horn ready to give the signal.
The entirety of the Royal Guard had been called into action: the Earth Pony forces were draped in the thickest, heaviest armour available to them and armed with heavy-duty lances; the Pegasi wore light-weight armour complete with steel-tipped wings designed to effortlessly slice through any exposed part of the enemy's body; and the Unicorns were dressed in garments laced with various enchanted gems designed to intensify their magical abilities and wore rings made of ruby and gold around their horns to induce a consistent magical defence against incoming physical attacks.
They were prepared for war.
The front line of Sunburst's demonic forces approached the city. Celestia raised her hoof to the sky and Luna promptly blew the war horn in response. The deep, bellowing sound of the horn rang loudly throughout the entire city, loud enough that it could be heard easily by Sunburst and his army many miles away.
Sunburst snarled, took in a deep breath and screamed "Charge!"
The Royal Guard stood their ground as the many winged creatures charged in the most direct path possible towards the city. As they grew closer, however, a beam of pink aura shot up from the castle grounds; it quickly cascaded over Canterlot, forming a protective bubble to shield the city away from the advancing forces.
Those in flight who reached the orb first tried various ways to penetrate it, from punches and kicks, to hurling their bodies against it and even biting it, but their efforts alone were in vain. The Pegasi of the Royal Guard fluttered just a few feet away on the inside of the orb, staring the enemy down in an attempt to intimidate. Meanwhile, an endless sea of creatures climbed the mountains below. Platoons of Earth pony forces - led by Unicorn Commanders - marched outward to the edges of the city limits in preparation of any breaches of the orb's defence.
Celestia and Luna flew up from their positions on lookout towards the outer edge of the orb, keeping a keen eye on Sunburst. To meet with the Princesses eye-to-eye, Sunburst created a platform out of his electric blue aura. As he stood upon this platform, it ascended into the air and glided effortlessly up to the perimeter of the orb.
"Princesses! As much as I appreciate the welcoming party, it really wasn't necessary." Celestia growled, but gave no further response. "What's wrong, Princess? I thought you'd be happy to see me! Your grandiose speech back in the Crystal Empire was inspiring!" Sunburst shifted his focus as he stroked the orb, "And what is this? Come on! Shining Armor's spell couldn't even protect you from changelings! What chance are they going to have against countless legions of the most sinister creatures from the bowels of Tartarus?"
The orange unicorn burst out laughing, "Of course, of course. You already know, don't you? You know you don't stand a chance, but you feel you have to put on a show to make it look like you're still in control. How many more ponies have to suffer before you surrender yourself to me, Celestia? Was the destruction of the Crystal Empire not enough for you? Was losing Princess Cadance and little Flurry Heart not enough? Look at you! You're heavily outnumbered! Your subjects know that, too, yet they're still so stubbornly obedient."
Sunburst grinned egotistically as he continued to berate the Princess, "Where's Twilight these days? Things go horribly awry and she just disappears. Where's she gone, Princess?"
Celestia spoke through gritted teeth, "I don't know..."
"No. I didn't expect so. It strikes me because there seems to be a lot of things you don't know! So let me ask you this: How much do you know about Typhon?"
Upon hearing that name, Celestia's nostrils widened, her heart rate increased and her breath quickened, "That abomination is nothing but myth! An old fairytale told many moons ago - nothing more."
"Your body language says otherwise, my dear Celestia. Typhon is very much real, and he shall appear before us in all his glory! Everything is in place for his return. All we need now is the sacrifice of the most powerful Princess in all of Equestria!"
In that moment, shouts and screams were heard echoing below them. A deafening rumble shook the air as the orb shattered into a million pieces all around them. The defences were broken. Thousands upon thousands of demons swarmed into the city both on foot and in the air. Sunburst and the Princesses stared off against one another as all hell broke loose around them.
Celestia was first to burst into combat. She dashed swiftly toward Sunburst, bearing her own set of steel-tipped wings. In the blink of an eye, Sunburst protected himself with a flash of his magic, deflecting the Princess' attack. Luna charged into battle, bearing her teeth as she attempted to help her sister. Sunburst, however, was very quick to respond, sending an intense wave of magic - like a magical sonic boom - in Luna's direction, unsettling the Princess' flight.
Below them, the battle raged. Demon and pony alike swung their weapons, brandished their teeth and swiped with their claws. The well-equipped Royal Guard had the upper-hoof; the Earth ponies thrust their lances through the chests of the enemy as the shields created by the Unicorns defended them. The opposing forces relied on sheer force of number to overpower the defences of the Royal Guard.
Felling a Unicorn would leave the Earth ponies almost defenceless bar their amour, making them the main targets. The demons relied heavily on the use of dark magic and necromancy to counter the Unicorns' protection spells and to revive fallen members of the Royal Guard and return them to the battlefield under their control to maintain their numbers.
Both sides saw a high number of casualties, but it had quickly become apparent that Sunburst was correct - the ponies were completely outnumbered. For each demon that fell, another ten took its place. There was no fight, and Canterlot was quickly becoming a slaughterhouse.
Meanwhile, the battle between Luna, Celestia and Sunburst raged on in the skies over the city. Sunburst quite easily fended off Celestia and Luna's attacks - no amount of physical force could break through his defences. The Princesses slowly grew frustrated and tired as Sunburst taunted them.
However, as the battle drew on, Sunburst began to realise the Princesses had refrained from utilising their magic during the fight; an unusual fact that irked Sunburst. He internally questioned the logic behind their tactics. He assumed the Princesses would have attempted to apprehend or kill him with their huge powers, but neither seemed to be the case.
Unwilling to let himself fall victim to some unknown scheme, Sunburst decided to stop toying with the Princesses. He fired a powerful beam of his aura towards the Princesses, rendering them motionless. His magic slowly caressed its way up the bodies of the Princesses, penetrating their horns and entering their bodies. The alicorns both fell out of the sky, crashing down into the fields at the foot of the mountain.
Sunburst swooped down to meet the Princesses at ground level. Slowly, they regained consciousness and lifted themselves up from the floor. They shook themselves down, removing bits of dust and grass which had gotten smeared on them from the impact. Sunburst realised his victory when the Princesses opened their eyes. Their irises glowed electric blue and their horns sparked the same colour as Sunburst's.
The unicorn brandished a sword at the Princesses from under his magician's cloak, "Kneel!"
Celestia and Luna knelt down on their front legs, bowing their heads, "We obey," they declared in unison.
Sunburst grinned, "Good." He glanced up at the battle which was now reaching its inevitable conclusion, "Canterlot is mine! Now do yourselves a favour and order the last of your guards to stand down."
The Princesses nodded, "Yes, Sir."
Sunburst watched as they took flight. He levitated himself high above the city, observing as the Royal Guards laid down their weapons, removed their armour and surrendered. Only a few hundred ponies remained, each surrounded by hordes of demonic creatures waiting orders from their commander... and Sunburst was all too willing to give them. As the Princesses flew back to his side, he smirked, using his magic once more to project his voice to the entire city, "Canterlot is ours! Soon, Equestria will belong to us!" The crowds cheered, "Now is your time to show the same contempt these ponies have shown to all of you: execute each and every single one of them!" he bellowed.
The ponies trembled in fear as they were all descended upon. Some chose to fight, whilst others simply accepted their fate. For both, the end result was the same; there were no survivors.
Sunburst turned to Celestia and Luna, "Now you're under my control, perhaps you'll be a little more truthful as to the whereabouts of your dear protégé. Tell me: where is Twilight Sparkle?"
Celestia's answer remained unchanged, "I don't know."
Sunburst turned to Luna instead, but her answer mirrored Celestia's, "We do not know."
Sunburst screamed in a bloody rage, "Aaaaaargh! Fine! Tell me this instead: what are her plans?"
"We do not know," Luna reiterated.
Sunburst's frustrations grew. He wiped his hoof across his face, "Why didn't you use your magic against me?"
"We are bereft of our powers."
"Bereft? How? Why?"
"It was taken by Twilight,"
"Why?"
"We do not know,"
"So she's keeping even you in the dark about her plans?"
"We presume so."
"Clever mare." Sunburst lamented over the lack of information for a moment, "If we can't track her down then we'll have to bring her to us. Where is her dragon?"
"He was in the Crystal Empire when it fell."
Sunburst threw down his hooves in anger, "For Faust's sake!" He shook his head, "No matter. It's an easy fix. I can just go back and get him." Sunburst engulfed himself in his own aura and momentarily disappeared. As he snapped back into existence, he had brought Spike back with him. "See? Time travel. Easy."
Spike quickly realised he was hovering several hundred yards in the air. He began to panic, letting out a wailing scream.
"Calm yourself! My magic is keeping you aloft! You won't fall unless I will it."
Spike sighed in relief. The next thing he noticed was the Princesses. "Princess Celestia! Princess Luna!" He glanced behind the Princesses, witnessing the state of Canterlot. His mind started to overload with information, "Wait. What happened to Canterlot? Wasn't I in the Crystal Empire? What's going on?"
Sunburst ground his teeth at Spike, "Long story short: Canterlot and your Princesses are under my control, the Crystal Empire no longer exists and I travelled back in time to bring you here."
"B-back in time? How far in the future am I? Where's Twilight?"
"Precisely the question I wanted to ask you, little dragon."
Spike was angered, "Well how am I supposed to know the answer to that? You were the one who brought me here. I don't know how far we've travelled!"
Sunburst groaned, "I meant Twilight! Where is she?"
"I dunno! She never told anyone what she was doing!"
"Can you still send her messages?"
"Of course. When I send stuff, I just have to imagine the pony I'm sending them to and it goes straight to them."
"Good," A quill and scroll magically appear in front of Spike, "Spike; take a letter."
Dear Princess Twilight Sparkle,
It is with a heavy heart I must inform you that the city of Canterlot has been taken by myself and the forces of Tartarus. Thankfully, I can confirm there were two survivors: Princess Celestia and Princess Luna. Unfortunately, the rest of the city's population has been completely eradicated. A great shame, I think you'll agree.
I shall spare the lives of your Princesses under the condition that you meet me here in Canterlot. You have twenty-four hours to comply, or else I will tear down the whole of Equestria to find you. I hope you come to your senses and cease this pitiful game of hide-and-seek.
Yours faithfully,
Sunburst