"Oh crap." Luna curses to herself.
"I DEMAND TO KNOW WHO!"
Star Shooter pulls out his pistols and aims them at Celestia, "Golly goodness, that thar is fiery varmint. Take this ya piece of kindle!" He shoots shot after shot at the Princess. Celestia dodges the bullets easy enough but notices the unique bullets are shaped like stars and explode on impact, the door she came through is now merely ash.
The sun goddess then launches a volley of sunlight spears, piercing through the very wind itself. With a single jump, Star Shooter launches himself into the air. He doesn't fall down however, instead he stays afloat.
"Ya really think yer the only one with wings!?" He yells. After some thought he reaches another conclusion, "Well Ah guess you kinda are since Ah'm not exactly using wings raght now. But that ain't the point!" He shoots more stars at the Princess who dodges them once more. Before she can counter attack a burst of purple magic appears between them. Suddenly with a flash, Twilight Sparkle stands in between the two fighters. She turns to Princess Celestia with a hoof extended.
"Princess Celestia! You shouldn't fight him!"
Celestia frowns, "Twilight I don't think you understand the gra--"
"Allow me to help!" With that said, purple fireballs emit from Twilights horn and float their way to Star Shooter. Too surprised to react, one hits him in the face sending him through the throne of the Day Court, destroying it.
Celestia jumps up and down giddily, "Whoo! Go Twilight!" The calibration is cut in half by a sudden vibrating sound resonating throughout the building. With that Twilight goes flying past her mentor and right outside the castle. Celestia turns to see that Star Shooter has his fist extended from his powerful punch.
"What? Ya didn't think Ah could use my hands Princess?" With that he brings his pistols around and shoots an entire constellation. One careful dodge and Celestia is once again out of the way.
By now the castle is already beginning to break down. The group of stars destroys the final foundation. As the entire building collapses Luna and Celestia use their combined powers to teleport everyone outside. As soon as they do this however, a pair of hooves collide with Stars face.
"Ya think yer the only cowpoke around?" Applejack's voice yells with a rage only an honest pony could acknowledge. Using her lasso she begins tying him up. Then...
"...wait...what happened?"
"..."
"Hey! What happened!?"
"Mmm."
"Did you just stop writing?"
"MmmHmm."
"But why!? You had a good story!"
"Meh, wasn't feeling it."
"AAAAARRRGH!!!"