Of all the spells that Twilight knew, Magefire was not the most impressive. It was neither particularly difficult nor time consuming. It took little to no effort with only an hour of study and practice. When she got around to learning it, she filed it away in the back of her mind as knowledge that would likely never be used; to Twilight, however, useless knowledge was still knowledge, and therefore valuable. In almost seven years, she never gave the spell a second thought.
It wasn't until Rainbow Dash had inquired about a spectacle that she was planning for a Wonderbolts tour in Canterlot that she dusted off her memories of it and gave it a shot again. It was the ideal choice for what it needed to accomplish; it was simple to cast, it wouldn't go out until she put it out, and it could be altered into any color the choreographer so desired. The perfect trick. Plus, Pinkie had told her it would "further the plot".
Everypony in the stadium that day seemed to be rather taken by it, so Twilight was willing to admit that Pinkie was, as usual, probably right about that. One pony in particular was the most impressed. Or distracted, depending on who you asked.
Captain Spitfire of the Royal Equestrian Air Force, Thirty-Eighth Fighter Wing, HAWC Division, at the time assigned to a public show team, callsign "Wonderbolts", would be the first to tell anypony who so dared accuse her that she was not the type of pony who would, or even could, get distracted. Especially not during a show that she had personally scheduled to provide the greatest possible spectacle in the most wonderful of fashions for the birthday celebration of Princess Luna herself. Such an important occasion needed to be free of all flaws. In the air, there would be no compromises made to perfection. No distractions would be allowed.
Not even Princess Twilight Sparkle, turning the sky into impossible shades of every color of the rainbow. The air around her burned with colors she didn't have names for. Spitfire caught herself without breath, unable to begin to comprehend the sheer beauty of the way Twilight bent nature to her will. It was utterly magnificent, to the point that it achieved what many creatures around the world would have thought to be impossible.
The spectacle that night left Spitfire completely speechless.
In almost one-hundred combat missions, nopony saw the captain flinch. Over her career as the commanding officer assigned to the Wonderbolts show team, she'd always exemplified the unwavering spirit of the Air Force. She'd been attacked and harassed by fans, met with nobles and princesses, and personally saw to the training of hundreds of recruits who thought they had what it took to be Wonderbolts. Through countless trials and tribulations, Spitfire stood tall. She never stuttered or mumbled, never slouched, never compromised. Spitfire never broke.
Not until she met Princess Twilight Sparkle that fateful night. She'd met the princess a few times before, and seldom at her best. She was disrespectful to her station at Rainbow Falls, she was cold and distant at the Wonderbolts Academy. If she was one for poetry, she'd tell her children one day that it all made her see her princess in a new light, acknowledging the irony for herself. She was not, however, prone to poetry, so she'd end up calling the whole ordeal hot.
She stuttered when she approached the royal. She mumbled for a while about how beautiful the light show was. She stumbled through her greetings and partings, then tripped over a few drinks. It was probably the single most embarrassing conversation she'd ever had in her life. After all these years, she finally broke.
Imagine her surprise when Twilight wanted to talk to her again that night. She came to the bar, sat down, said hello, using her hoof to gently brush a few strands of hair away from her eyes. They talked, and with a few drinks in her, she finally opened up. The night went on, ponies went home, the castle staff cleaned up, but Twilight and Spitfire talked. Eventually, a guard came to kick Spitfire out of the ballroom. Twilight followed. They wound up in Twilight's quarters, unwilling for the night to come to an end.
They met later, again. They flirted and teased, then dated and courted. They fell in love, over years, and were to be wed, thanks to that fateful night.
Twilight forged their rings herself. Spitfire was a military pony, and thus couldn't wear the traditional hoof ring, so she made them as horn rings, tied around the chain on Spitfire's dogtags. She even went so far as to enchant each of them, something to show her wife how much she meant in her life. There was only one she had in mind.
Magefire would burn until she put it out. Magefire could burn in any and all colors, even autonomously. Possible most importantly, Magefire didn't give off heat; it pulsed, similar to a heartbeat. Long months, years apart, Twilight on diplomatic missions, Spitfire attending to her military duties. All they needed to do was hold their rings against their skin, and they wouldn't feel alone again.
And when Twilight held a ten-thousand year old ring in her hoof, it burned in the most glorious gold. It still pulsed, strong as any heartbeat. Above all, Spitfire's ring still burned, as it would, for eternity.
Twilight wanted to put it back in the jewelry box. She could put it back, go outside, and find her special somepony again. She kept saying she was going to propose that day. She just needed a reminder. Something to help her remember what true love felt like.
She didn't really need it. Alicorns don't really forget. But it was nice to feel it again. That sensation of her first love.
She smiled, and cried. With the soft push of her magic, she placed it back in the jewelry box, and let a single tear trail after it. Afterwards, she wiped her eyes with a hoof, and used her magic to reach into her beside table, withdrawing a small black velvet box.
He wasn't Spitfire, and that was okay. Twilight wouldn't forget, after all. But there were new memories to be had. Smiling broadly, she placed the box in her saddlebags and stepped out the door.
She owed Spitfire a lot. Thanks to her, Twilight Sparkle knew what love felt like. And thanks to Spitfire, she knew today was going to be a good day.