She stood upon the Wall that separated the City from the surrounding Wastelands and waited. She had felt the resonance from the pony's "Night" Origin and its clashing with her "Day" Origin. It was unusual to meet ponies with more than one Origin. Hers, as to be expected from being one with it was "Night." Her sister's was similarly "Day." until... well, the Empire.
She shook her head before blinking as she felt saw the explosion at the centre of the City, at the top portion of the Tower. It took a few moments before the spells keeping her and other undesirables fell. It was as if the world blinked, as she stopped existing at the wall and began existing on a rooftop near the Tower.
She watched as the debris was falling towards the ground, towards the nearby assorted group of security golems. She was about move on when she noticed a blotch of colour within the debris. She narrowed her eyes as they found the body of the pony from before. Sunset Shimmer. Yet another name added to the list her sister's hubris has taken.
As the world blinked and the one that was there before stopped existing, it could have sworn that for a short moment there was something watery and salty falling that evaporated before it hit the roof.
Continuing her existence in front of ornate doors, she blinked three times to clear them from any possible grime and opened the doors to the Empress Sol Invictus' chambers. Princess Luna's expression did not falter, as she prepared to fulfil her eternal Destiny and duty "Protect" just as her sister's, Princess Celestia's eternal Destiny and duty had once been "Serve"
Princess Luna entered her sister's chambers————
Terribly sorry there, my friend. But she wasn't our protagonist.