Gonna be honest I don't know how to write battle scenes so I'm just putting it down as best I can.
The bright colors of different ponies started to march onto the battle field.
Shining Armor and his commanders behind him with the seven ponies all dressed in cloths Rarity made for the occasion. It was camouflage armor with different pocket buttons to show whose it belong to.
Picklock looks out to see where he was noticing he was in the back of his army.
Each army was still as they could be. A few ponies were snorting and stomping their hooves onto the ground as they wait for orders from their commanders.
King Sombra let out a loud yell," Dare to go against me and my army?! You will soon regret your decision! Soldiers! Attack!"
The black army galloped forward heading towards the combining army.
"Steady now! Wait for my signal," Shining Armor yells and watches the army progressing toward them.
Once the army was only a few gallops away he yells," Now!"
Then each unicorn pony started to fire opposing shots at the black crystal ponies making them shatter like glass but the army kept galloping forward.
Then with a sound like thunder the two armies clashed!
Ponies and the black ponies each going down with a fight and medic ponies teleporting in and out of the battle to get the wounded cared for and back onto the field.
Shining Armor and his commanders joined the fight a few minutes later with a group of unicorns charging in piercing at the dark crystal ponies.
Though the battle looked like an easy win it would not be so.
With each black crystal pony going down however two come up in its place.
The seven pony friends watch in horror as the battle progresses.
Noticing this Picklock looks out onto the battle field to see where King Sombra was.
She found him surrounded by some of the ponies with golden armor. She points down to him," There he is! Cover me!"
She gallops forward and her six friends gallop with her heading towards the battle field.
Pinkiepie just jumps on the dark crystal ponies making them fall and break and Applejack uses her bucking skills to kick the crystal ponies away from them.
Rainbow Dash kept to the skies keeping an eye on King Sombra as some of the dark crystal ponies attack her as well. Rarity and Twilight uses their magic to keep King Sombra's soldiers at bay.
Fluttershy had gotten into a few tight spots as she tried to keep up with the group. When a dark pony almost attack her she yelled and closed her eyes shut before she realized that she wasn't hurt.
Looking she saw Discord in front of her growling," What is with the commotion party?! Fluttershy you didn't even invite me how rude!"
Fluttershy gives him a hug smiling," Thank you Discord but now's not a good time to explain!"
Discord sighs sarcastically and looks around at the dark ponies," Hmm…I wonder if I could use them in my stain glass shows?" He started to pick each dark crystal pony up and made them into a stain glass then showing them off one at a time like a Picaso painting.
Meanwhile Picklock was dodging and zigzagging through the battle to get to King Sombra.
When she finally sees him she rushes to him only to stop when she saw he was battling Shining Armor.
They were horn to horn and King Sombra had the better advantage of Shining Armor. Sombra knocked him onto the ground.
Sombra was about to take the final blow when Picklock rushes in.
His horn pierced her almost near her heart.
Using the opportunity she places a hoof onto his heart and says," Though closed to the world your heart maybe. Let it be open for me once again."
Then a bright light came from both of the ponies blinding all the ponies around them making the battle stop.
Ok I added Discord just to be random! Hello? It is Discord after all! Lol!