@Catpone Cerberus
The scenery of the battle would play over the course of what felt like hours. In reality, only a few minutes had passed. Sombra's visionary magic that took over her mind in this moment was very much like a very vivid dream. Una would notice a few key details. Sombra's army was losing. The enemy Equestrians had continued to advance forward towards the City over the course of the hours as they passed. The fighting only got more brutal and more desperate as his armies were forced to fight a losing battle in which they were outnumbered.
Equestrian soldiers outnumbered Sombra's soldiers 4 to 1. Despite this, his forces continued to put up a good defense. Unfortunately for them, this was not enough. Una could see many of his soldiers having shared similar fates. Shot at by unicorn magic. Blown up in Aerial Bombardments. Stabbed to death by charging Equestrian soldiers. Sombra's emotions continued to get more and more enraged as time gone on. The explosive nature of his hate caused him to eliminate many Equestrians at a far quicker pace than before. They kept coming.
Sombra and his troops would fall back to make a final stand within the city itself. Civilians fled or hid underground as the bloodshed came into the streets themselves. Sombra's dark magic managed to stall the Equestrians for a short time, allowing his soldiers to regroup in one final attempt to push the Equestrians out of the city. This was the most brutal part. Sombra's soldiers could be heard fearfully giving their lives for their King. Many of them, despite being brainwashed - were still able to scream as their lives were ended. Sombra did his best to stop this, showing his pure brutality in defending his city here. It wasn't a sight for the timid. It was sights like that out of a nightmare. The screams. The agony. The pain. And the blood. All of it was something that filled with him the most pure, raw, and utter hate there was.
Then the Equestrians started to bomb the city. Bombs were dropped on remaining troop positions, and Sombra's remaining troops would make a motion to flee for the hills. Sombra agreed with this and was about to lead them out of the city to retreat elsewhere and go into exile. That was when the two sisters showed up. Celestia and Luna, in full battle armor.
They caught Sombra off guard while he was fleeing. There were no words exchanged. The looks on their faces and the battle that ensued spoke volumes more than words ever could. Sombra, a dark tyrannical King as he was, was valiantly defending his source of power from outside forces. Celestia and Luna were harsh to him. In their eyes, he was a threat to be eliminated at all costs. Sombra felt the same about them. He wanted to make them pay for this.
Sombra tried all sorts of things. Illusions. Shadow magic. Dark Magic. Only being able to subdue the two sisters for a short timeframe before they would inevitably come back. Sombra would receive blow after blow. Una could feel the pain Sombra felt. The agony. The agony of having to lose everything, and to fight for one's life in the face of a superior opponent. Sombra would inevitably be slammed up against a wall, his body, nearly broken - but still fighting.
In a last ditch effort, just as the two sisters were about to charge at him for one final time - Sombra's horn lit up, and with all of his power, he himself would banish the Empire away into Limbo. The Empire, all of it's buildings, his soldiers, would all suddenly vanish.
If he couldn't rule - then he would ensure that nobody could.
And like that, he faced a blinding light, as his body was evaporated into light for the first time. The pain was indescribable. It was absolute agony. Overwhelming agony. Una could hear Sombra's horrible screams.
And like that, all went to black. An undefinable amount of time later - Una would see Sombra in his banishment. Nothing but blackness. A very faint sense of awareness. But only agony. Hate...and loss.