The first incling that Sandbar had that something was wrong was the school emergency alarm going off. It was so loud that the ground itself shook as it sounded, causing ponies to bounce and wobble all over the place.
Pinkie Pie, in particular, seemed to take full advantage of the vibrations. "HeEeEy! ThIs MaKeS mY vOiCe SoUnD sIlIy!"
"Pinkie, we don't have time to waste!" Starlight called, as she threw open the door. "You are needed in Canterlot immediately according to the Magic Telegram I received. The country is in real danger!"
"OK!" Pinkie replied, completely forgetting what had just happened, and running for the door. The students filed out of the door and headed for the atrium.
"Attention students. This is not a drill. Please report in an orderly manner to the atrium immediately. I repeat; Attention students. This is not a drill. Please report in an orderly manner to the atrium immediately."
Sandbar pushed through the crowd to find his sister, Cozy Glow, looking very worried. "Is this a fire alarm test?" she asked. "I thought we had those on Friday's!"
"Attention students. This is not a drill. Please report in an orderly manner to the atrium immediately. I repeat; Attention students. This is not a drill. Please report in an orderly manner to the atrium immediately."
"We heard it the first time!" Smoulder snapped. "And the fiftieth too."
"This is no drill alright," Sandbar said, grimly. "It sounds as though something is very, very wrong."
The students finally marshalled in the school atrium, where Starlight stood on the podium. She was standing alongside Councillor Trixie, who looked equally worried- an emotion one usually didn't equate with the master magician.
"Morning students," Starlight began. "There isn't much time, so I'll be brief; this morning, we received reports of three armies attacking Equestria. One was approaching from the north, another from the south, and another from the west. We have no real details on the armies in the north and west, but the Pillars attempted to intercept the one approaching from the south."
There was silence from the students. But the country coming under attack seemed to happen every other weekend.
"Unfortunately, the Pillars were routed, and Somnambula only just managed to get to Canterlot to warn the Princesses in time. Worse is that the direction and speed of the western army has been calculated. This school is right in its path."
The students collectively gasped. "We're gonna die!" shouted one, and the crowd erupted into confusion and pandemonium.
Trixie took the microphone. "Calm down!" she shouted. "The great and powerful Trixie shall see that you come to no harm."
"Which brings me on to my next point," Starlight replied. "I want all of you to report to the underground bunker immediately and await the all clear. Until then, you must not leave the bunker. Do I make myself clear?"
"Yes ma'am," the students chorused.
"Good. Now let's get moving!"
The bunker sat on the western side of the school, buried underneath the library complex. Constructed of Crystal Empire alloy, it was virtually indestructable; a similar structure had been tested by detonating a megaspell atop it, and whilst everything in the testing area had been flattened, the bunker and its contents had emerged undamaged. When facing a potential invader, this was the safest place to be.
"All students, remain calm and follow Councillor Trixie's instructions," Starlight reminded them. "Stay in groups of six and do not run. Remain calm, this will all be over soon."
"Oh, it will indeed," said a familiar voice. The Young Six, who were yet to get into the bunker, turned around in shock when they suddenly saw the wall be blasted open by sustained gunfire. Into the space buzzed several Changelings, but unlike any that they had ever seen before (which was, admittedly, three or four). These Changelings had gunmetal chitin and were covered from head to tail in thick, blue armour plating that looked to be at least four inches thick. The wings were also noticably larger than on most Changelings, but this wasn't the most alarming figure.
The next being to arrive was Queen Chrysalis herself, and to say she had changed was an understatement. Each of her four hooves were now protected by greaves that glowed a sickly turquoise to light green, and heavy turquoise and blue armour plating had been added, bolted into her elytra and around her chest, protecting the front and sides. Her crown extended down the sides of her face as deflection plating, and the edge of her horn and her eyes glowed a sickly green.
"It's been so long since I was last in here, trying to awaken my army." she said. "It wasn't the cleverest of ideas for the architect to put the bunker entrance and the access chamber for the Tree of Harmony in the same place."
"How does big bug thing know access chamber for bunker?" Yona asked, confused.
"You showed where it was to the new teacher during induction week, remember Starlight?" Chrysalis asked, a smirk on her face. "Of course, I looked rather different back then."
A look of realisation washed over Starlight's face. "Shutterbug," she whispered. "We had been infiltrated this entire time... and I had no idea."
Several of the Changelings fired off explosive bolts that blew the hydraulic pistons holding up the bunker access door, which slammed shut. The Young Six were trapped on the surface.
"Right, run!" Gallus called, and they sprinted for the door. They had to get back to the place they were before. Minutes later, Changelings buzzed after them as they heard the sounds of heavy weapons fire in the library. It sounded as though Starlight had engaged Chrysalis and her guard.
"This isn't how I'd planned to spend reading week!" Silverstream cried. "I was thinking of going home!"
"That's hardly our biggest concern right now, Silvs!" Smoulder shouted. "We need to get away from these buzzing things."
As they sped along, Ocellus could read full well how everycreature was feeling. The prime emotion she was tracking was fear, with a healthy dose of trembling, when suddenly she stumbled as a massive blast of pain shot through her skull. She cartwheeled through the air, taking out Yona in the process, and she suddenly crashed through a door and into another room.
"Ocellus!" Sandbar cried. He stopped, turned around, and suddenly went back the way he came, bucking open the door and then slamming it shut behind him. "What's going on?"
Ocellus rubbed her head, seemingly in a lot of pain. "There's too much!" she gasped. "Splitting... headache... hive mind... Changelings to intercept princeps... Synapse link..."
Suddenly, Sandbar remembered something that Chrysalis had said the previous academic year down in the pit below the school.
"That's right. Ocellus was bred from the purest of genetic stock I had as a backup should I ever be pushed into a corner. She is no normal nymph- she is a Princeps class of Changeling."
"Wait a minute!" he said quickly. "Ocellus, you've tapped into the local hive mind!"
"B- but normal Changelings can't do that!"
"Remember what Chrysalis said? You're a Princeps. Like Praetors, you have a localised synapse connection that allows you to access and control local assets in times of need. If you can read what these Changelings are up to, you can potentially redirect them and give them different orders!"
A look of determination formed on her face. "I'll try," she replied. "You can mess with me, but you don't mess with my friends." She focused, incredibly hard, the effort clearly quite the strain, until she very suddenly flashed blue in a pulse of energy.
When the light cleared, Ocellus was glowing, her eyes lit up as data and telemetry from the armoured Changelings in the area was fed into her enhanced synapse network. "OK, that's the local network created. Time to have some fun!"
Meanwhile, Gallus, Smoulder, and Silverstream were flying through corridors with more of those strange Changelings flying after them.
"You don't think these are the Changelings that Chrysalis tried to wake up with the artefacts, right?" Silverstream asked.
"Maybe?" Gallus replied. "Doesn't matter anyway, what does matter is not getting zapped!"
Suddenly, the Changelings chasing them seemed to lose all sense of direction, and then crashed into another set flying the other way before smacking into the ground, dazed and surprised. More Changelings looked increasingly confused, with some more up ahead stumbling round in circles with others standing there idle.
"What's going on?" Smoulder asked. "They've all stopped!"
"Are you guys OK?" called Sandbar, as he and Yona, as well as Ocellus, caught up to her.
"The Changelings suddenly stopped attacking us," Silverstream told them. "It's all rather confusing, really. They suddenly stopped." She looked at Ocellus. "Ooh, what happened to her?"
"She's created a localised hive network via a synapse link, and is using that to direct the Changelings into doing nothing."
"How can she do that?" Gallus asked.
"She's a Princeps, remember?" Smoulder said.
"More than that, Ocellus our friend!" Yona called, a sentiment they all heartily agreed with.
"OWWW!"
Sandbar suddenly saw Ocellus fall over, and start to stumble, so he galloped over and popped her up. "Celly? What happened?"
The Changeling rubbed her forehead. "Oww. That really stings. Chrysalis suddenly pulled the plug on my connection. I think she and the other Changelings have teleported somewhere else, but I was able to download a fair bit of data before the connection was lost- including what she's been up to the last few months."
"What do you see?" Silverstream asked. "This could help us fight back!"
"OK, let's see," Ocellus replied. "Being teleported to a cave, meeting Grogar, Sombra goes off and gets killed but blows up the Tree of Harmony in the process-"
"So, this Grogar guy was pulling the strings on that?" Smoulder asked. "Figures. He is the embodiment of evil, after all."
"Less talking please," Ocellus replied. "It makes processing the information harder. I remember now. Being sent to get the Bewitching Bell, spreading chaos in the Canterlot region to make ponies distrust each other, taking the power of the bell alongside Tirek and Sombra to make themselves extremely powerful, draining Grogar of his mag-"
She stopped. Her eye twiched momentarily in disbelief.
"GROGAR WAS DISCORD THE ENTIRE TIME?!"