Tempest took a deep breath, trying to keep her infamous cool.
She hadn't expected "turning good" to be such a simultaneously easy and complicated task. Something deep inside of her had changed when Princess Twilight had saved her life. She had felt... broken when the Storm King had betrayed her. She knew that she had nothing more than the quality of her own service to serve as a testament that he would keep his word, no choice but to place what little trust she had in him and his quest for power. Had she known then that relying on him would prove to be such a mistake, she would have blown him to oblivion that day they met at the heart of a blizzard. But even by that point, she had lost so much of herself to her quest to restore her horn that it hardly mattered. Even the slimmest chance was worth digging in her hooves and fighting tooth and claw for. She would find what she had lost, or she would lose herself completely in her quest. Unfortunately, for a long time, it seemed that only the latter had occurred. Or so she had thought.
But when Princess Twilight had saved her, she felt something for the first time in ages. Something all her own, independent of the Storm King and completely separated from her quest. It was the first time her thoughts had strayed from becoming whole again since she'd left Equestria as a young filly. She had taken a gamble, seizing on that feeling and letting it guide her ever since.
She hadn't fought when the royal guard had taken her for questioning and trial. She had accepted her failure, and wanted to atone for her actions. She had been willing to go to prison for her crimes if other ponies said it was the "right" thing. She'd lost sight of right and wrong a long time ago, her judgement was flawed and her vision skewed.
She also had felt absolutely no need to fight when Princess Twilight and her friends had burst into the trial, all willing to vouch for her "character."
She may have been penitent, but she wasn't stupid, after all. Prisons were awful, she'd broken out of several.
With Twilight's appeal and the six guardians of Equestria all pleading on her behalf, to Tempest's complete shock, she had been granted amnesty for her crimes, completely absolved from her actions under the Storm King's orders. The verdict had resulted in an altogether unpleasant group hug, followed by an invitation from Twilight to join them in her castle in Ponyville. Judging from the slight edge of desperation in her voice, Tempest wondered just HOW empty the castle had to be. She had politely declined the offer, claiming that she needed time to adjust to the idea of being back in Equestria. The Princess of Friendship had been, quite thankfully, sympathetic to her hesitation and left her with an open offer... and a list of sightseeing destinations in Canterlot.
Tempest was hesitant about being given orders so soon after being betrayed by the last person whose orders she followed, but she decided to give Princess Twilight the benefit of the doubt. The seven libraries on her list were silently and discretely trimmed down to one. It was admittedly a pleasant place, but perhaps too quiet. A little background noise helped Tempest not to feel quite so alone with her thoughts. Inevitably, though, the thoughts had come to her, following her though mile-high stacks of booths, stalking her down garden labyrinths and hiding behind her reflection in shop windows. It was in every dirty look she received on the street, every guard that tensed when they saw her.
No ponies had died in the invasion. Thankfully, that wasn't the Storm King's style. He didn't kill if he could avoid it. There was always treasure to be moved or merchandise to be shipped, and the airships needed constant maintenance, as well. There was no use to killing when fresh recruits and new slaves were so much more useful. The city itself, however, had suffered immensely. Entire blocks had been systematically looted for any valuables, houses ripped apart in search of secret safes and hidden treasure. The population had not been diminished, but their city had been ravaged and their homes torn to pieces. It was all her fault. She had told herself that the king would have come to Equestria eventually, no matter what her actions in the past had been.
But she could have warned them. She could have come home and told the princesses of the creature that had conquered half the world before he'd heard of Equestria's near-boundless magic. Heard it from Tempest's own spiteful words. Thankfully, over the years, she had become good at avoiding thinking about the past, and pushed back those thoughts every time they caught her, forcing herself to the next location on Twilight's list.
Her greatest surprise had come when, after nightfall, she had spied on the changing of the guards at Canterlot Castle. The Day Guards had been dull and boring, she had never seen a wider collection of numskulls outside of the Storm King's army. When the Night Guards had come to replace them, though, her interest had been immediately piqued. For every Day Guard, there was a Night Guard to replace them. Rather than the bulky, musclebound stallions making up Celestia's guards, Luna's forces were smaller, sleeker, and better suited to the darkness, much like Luna, herself. Most had dark coats and bat wings, though she thought she could make out a few unicorns patrolling the streets, as well. Their yellow eyes glowed in the darkness and they were much more observant. Each guard acted independently, sometimes moving with a partner, but they were much more difficult to predict. They had little supervision, and she could tell from their predatory stance that they weren't just looking for trouble to stop, they were hunting for it. There was no silent vigil, only stalking shapes in the darkness, each waiting,daring for a pony with the gall to think darkness would hide them from justice.
She had honestly considered challenging one or two of them to test whether or not there was a difference in their fighting abilities, but she didn't feel like pressing her luck when it came to being thrown into a jail again.
She picked out a pair of guards and followed them through their shift. Unlike their daytime counterparts, they had spent a lot of their time joking and chatting when all was quiet and peaceful. It was obvious that they were good friends on top of being coworkers. Ordinarily, she would stomp out this kind of frivolous distraction in the ranks she commanded. However, friendship had served Equestria well enough in fending off the invasion, so se was willing to once again give it the benefit of the doubt.
She'd found a military-esque group that tended to keep out of the public eye, and would most likely meet Princess Twilight's mandatory quota of friendship. It seemed like a perfect place for her to begin her fresh start. The next day, she took a train to Ponyville to tell Twilight of her plans.
To her surprise, Twilight had been completely on board with the idea, enough so to make Tempest suspicious whether there was something about the Night Guard she didn't know. Without any certainty Twilight was hiding anything from her, however, she began the application process.
Over the course of the next week, she tried to leave Twilight's castle a total of three times, each time resulting in the residents of Ponyville scattering once they'd caught sight of her, and Princess Twilight having to tell the local police force of the town to stand down. All of Twilight's friends were frequently coming in and out of the castle, but none of them seemed to live there aside from Twilight's student, Starlight Glimmer. Starlight had been the only pony so far to catch the hint that Tempest wanted her space, and the most reasonable pony out of Twilight's entourage. If Tempest had planned on taking permanent residence in the castle, she wouldn't have been surprised if Starlight had been one of her first friends.
After a week of waiting, however, her application returned. To her surprise, it had been approved. Twilight's smug grin, however, informed her that it most definitely had not been an accident. She had been ordered to report to some place called the "New Lunar Republic" for her training.
She hadn't realized Equestria was outsourcing their military training, now.
Of course, that wasn't the case. Twilight had quickly explained that the New Lunar Republic was the organization that trained and supplied night guards to Canterlot, as well as being tasked with missions straight from Princess Luna, herself. Their focus, she said, was on subterfuge and neutralizing domestic threats. That explained why there had been so little resistance from the Night Guard the day the Storm King had attacked: they had not only all been asleep, but their whole organization was dedicated to dealing with... subtler threats than an oncoming army.
Twilight and her friends had offered to accompany Tempest to the Plains of Lore, where the base she'd been ordered to report to was housed, but she had politely turned them down. She'd grown well used to traveling alone and one last sojourn to collect her thoughts was just what she needed. The directions to the base had been simple enough to follow, and the trip was boring to the point of being mind-numbing, but it gave her enough time to come to three conclusions.
One: She was going to atone for her actions against Equestria.
Two: She was going to leave behind her past, and focus only on moving forward.
Three: She was going to prove that Twilight's faith in her was not in vain.
Now, she stood in the doorway of the underground facility, staring her future in the face. She wasn't frightened, nothing ever frightened her, but she would admit (only ever to herself) that she was feeling some trepidation. This was her second chance. This was it. If she messed this up, she would be finished, most likely never able to show her face in Equestria again.
Luckily, Tempest's ability to keep her cool was infamous.