Dark Empire

Twilight observed the pile of rubble blocking the entrance to the tower. This wasnt a little pile of debris made of little hunks. There were large sections of wall, ceiling and archway. They were not going to move much of this.
"We can't move this aside. We need to find another way in."Twilight looked around.
"Like the tower barring the way here..."Rarity sighed.
"Yeah."Twilight blinked. Celestia, who was busy trying to maintain the little order she had in the ruined Palace, overheard and turned to her student.
"There is not much in here. Try looking around. Maybe there's something you can use to help."Celestia suggested.
"Good idea Princess."Twilight nodded.
"Ah think a sledgehammer could do a mighty load to help get in."Applejack tapped her chin.
"Assuming we're trying to move the rubble. Wouldn't you think the Princess or a Guard would have thought of that?"Rarity asked.
"Rarity has a point."Fluttershy nodded.
"There's a couple of corridors. We should make sure there's nothing of value in them."Twilight gestured.
"Ah agree."Applejack nodded.

~~~

Twilight heaved at the door. It wasn't barred or stuck in the ground but it was tightly sealed.
"Need help?"Celestia asked, inspecting what Twilight was doing.
"If you're offering."Twilight smiled.
"Of course."Celestia's horn lit up.
"The lock is broken, but intact enough that it has sealed the door. Hold on."Celestia explained. Twilight watched as she struggled with the lock, a glow coming from between the doors. Eventually Twilight heard a snap and the pieces of lock falling to the ground. Twilight and Celestia then put their magic together and heaved at the doors. They slowly ground open, but when it opened a bit the ceiling cracked and dust fell down.
"I think that's open enough. Too much of this Palace, let alone Canterlot, has collapsed already."Celestia gestured for Twilight to go through.
"Thanks Princess."Twilight grinned.
"It's nothing. But I must return to my duties."Celestia nodded, turning and walking away. Twilight walked through. It WAS an apartment, from the looks of it. She walked over to the cracked window. Trying to see through the dust coat, she only managed to spot a squad of creatures inspecting how to pass the fallen tower. They muttered a little, but Twilight couldn't hear, so she creaked the window just a little, and pressed her ear against the gap.

"We must bypass this barricade."
"How do we know it is a barricade? It appears to be a fallen structure."
"Shush! It still ACTS as one, and thus IS one."
"Okay, okay."
"How do we pass it? We cannot jump over NOR can we move it. There is likely to be no tunnel."
"Maybe if we can't move it or get over it..."
"What are you thinking ?"
"Maybe we can blow our way through."
"What do I suggest?"
"Looking at the brittle material this is made of, a Structural Disassembly shockwave should do the trick."
"Of course. I will get the gunner."
"Good."

Twilight heard enough. They were going to break into the Palace! Everypony was in danger! She ran back towards the half-open door, but she stepped in the crack she had stepped to avoid and it gave way under her beating weight. She crashed into the now debris-filled room. This had obviously gotten the creature squad's attention.

"There are occupants in this building!"
"And?"
"We must hurry to silence them before they can be alerted of our presence. Quickly now, let us bypass this barrier!"

Twilight scrambled to her feet, but shook and fell again. Looking to the cause, she saw her leg was broken. The massive inrush of pain suddenly caused her to scream, catching the attention of an already-alert Celestia. A second later and the solar princess was at the edge of the hole.
"Twilight! Are you alright?"Celestia asked.
"I broke my leg!"Twilight answered, nursing the awkwardly twisted limb.
"Guards! Get her out of there!"Celestia ordered the two guards that had followed.
"Hang on..."Twilight hobbled to some dusty parts at a hole in the wall. It was vaguely arranged to shape a device that, if a part is removed, a rope springs forward and could launch projectiles. She moved a piece or two into better positions.
"Do we have spare spears?"Twilight asked. A few moments later and she was buried under a few dozen spears.
"Okay, hang on..."Twilight moved to point it at a creature and removed the hunk of wood stuck in the plank that formed the body. Indeed the spear that had loosely sat there originally launched off at high speed, beheading the creature. With a smile Twilight heard

"We've been spotted! Quickly, hurry!"
"A Structural Disassembly shockwave takes time to prepare!"
"I don't care! Hurry it up!"

Twilight moved back a little.
"Twilight, you're a genius! Guards, after as many spare spears as we have and bring them here. Station a soldier here to operate the contraption! Twilight has found us a defense!"Celestia ordered.

Quickly enough a Guard helped Twilight out of the hole, as another ran to the contraption, which humans would know as a 'crossbow', and started firing at the panicked creatures. A few shots later and the squad were all headless. A moment later and the pile of spears grew as a few dozen more spears were thrown to the Guard down by the crossbow.
"Thank you, Twilight. Now we have a way to fight off these monstrosities. Here."Celestia smiled. She gingerly lifted up Twilight's broken leg with her own and her horn glowed. Twilight felt several uncomfortable clicks before Celestia's horn stopped glowing.
"I've fixed the bone, but the wounds are still there, but I need to save what energy I have."Celestia smiled.
"Thanks, Princess."Twilight smiled back.

~~~

Applejack listened to the crash through the wall. She and Rarity had once again taken this route, while Fluttershy stayed behind to take care of injured Guards in any way she could.
"Hear that? Ah hope Twi's alright."Applejack tapped the wall.
"Indeed. She's a valuable ally in this crisis and we cannot afford to lose her."Rarity nodded, peering out the window at the forsaken Canterlot.
"I've always wanted to come here, maybe to live here, but I've only ever been on short visits. And then before I can THIS happens."Rarity sighed.
"Look Rarity. Sometimes bad things happen we don't want to happen. It happens to all of us. Maybe they'll build a new Canterlot, just like the old one."Applejack put a reassuring hoof on Rarity's shoulder.
"But right now we need to focus on the task at hand. Luna is in trouble and we need to find a way to her, and then there's Equestria we need to save."Applejack added. Rarity turned away from the window, to Applejack.
"You're right. I've done enough being sad and all. We need to save Luna, and then Equestria. So let's go."Rarity's face gained a look of determination. Applejack simply smiled in response.

~~~

"There's nothing in this hallway except for that room that collapsed."Twilight tapped her chin.
"And we still need to find a way into that tower."Twilight added.
"And how do you suppose we do that?"Celestia asked.
"Well we can't get through that debris. Maybe if we get onto the roof we can find a hole and get in through there."Twilight suggested.
"Good plan. Also it's unlikely any of our enemy can get onto the roof to get in."Celestia added.
"Right. Maybe a staircase. Fallen bit of roof."Twilight tapped her chin more.
"Twilight! Maybe if we let the ceiling above that door collapse we will at least have a boost!"Celestia grinned, looking to the doors.
"And also it wouldn't completely block off the way to the weapon!"Twilight grinned also, gesturing to the Guard keeping an eye out from the crossbow.
"Guards, hold on. We're collapsing a bit of roof."Celestia raised her hoof to hold any Guard movements.
"Why, your Highness? Would that not let the enemy in?"A guard asked.
"No. I doubt they can jump the entire way up there, and also it is near impossible to climb. It will allow us to get to Luna, hopefully."Celestia answered.
"Alright. Men, stay back! The Princess and Twilight are making a way to Princess Luna!"the Guard stepped away.