By the time that Spike and Starlight finish taking the absurd number of measurements Twilight demands, the princess had time to calm down sufficiently from her earlier reaction to her uncanny transformation. At least, until she incinerated another stack of papers- At this rate, Spike wonders if there will be any books or papers left over by the time this whole situation was dealt with.
"Alright, Twi, come on, we're going outside." Spike states in a dull voice as he tugs on Twilight's shoulder, trying to direct her away from the pile of ash she is currently desperately trying to put back together.
"I'm a walking fire hazard! I'll burn down half of ponyville at this rate!" Twilight cries out, oblivious to Spike's attempts. After a few too many attempts, Spike finally relents to using a new tool available to him; Focusing, he pours magic into his horn just as Twilight had taught him, and levitates Twilight off the ground, finally catching her attention as she floats over to him.
Grunting with effort, Spike offers Twilight a strained smile. "Yeah, you will. Exactly why... You need... To go outside with me!" Spike lets twilight down, panting- Magic is hard!
Twilight blinks at him confused, but does follow after him as he leads the way to the clearest balcony the castle possessed, a thankfully quite large, flat, and non-flammable place. "I don't understand, why did you want me up here?" Twilight asks, looking around.
Spike takes up his position on the far end of the balcony. "You helped teach me how to walk and use my magic. Now it's my turn to return the favor and get your fire breath under control." Spike states, authoritatively, feeling a distant sense of giddiness deep down. It is definitely a special day that he gets a chance to teach Twilight of all ponies something new for a change.
“Fire breath? But what is there to learn? I just have to stop letting it out, right?” Twilight asks uncertainly. “Though, that is easier said than done...”
Spike shakes his head firmly. “Not that simple. You need to learn to control your breathing to keep it from mixing with your magic. Fire breath happens when dragon magic gets into your breath and mixes with the air, so you need to get used to keeping a handle on it.” Spike explains. “You’ve been letting a little bit of your magic out every breath you’ve taken since you transformed, and normally that doesn’t cause any problems. Without specifically focusing it out in a cone, there isn’t enough to react to cause a significant fire; it usually just dies in your throat. But if you sneeze or cough...” Spike coughs to demonstrate the point, releasing a quick-burning ball of green fire in the air. “that happens.”
Twilight gives Spike a surprised look. “Since when are you such an expert on dragon magic? You know more than I do! That... Never happens!” Twilight sounds both incredulous and tremendously proud.
Spike shrugs. “Eh, I guess your bookworm ways must have rubbed off on me.” The dragon-alicorn remarks coyly, before his expression turns more somber. “In all seriousness, though, I studied up on it after I burned that book of yours on accident. I read every book on dragon biology you had in your library, and combined with my own personal experience I was able to figure some things out.”
“Wow, Spike, that’s really impressive!” Twilight says, before nodding her head. “Alright, so how do we start? How do I control the flow of magic through my breath?”
“Well, it’s a bit different from unicorn magic, more physical. At least, from what I’ve been able to tell since I transformed.” Spike explains. “Try to start by just focusing on your breathing, how it feels. Take some deep breathes in and out, until you can feel all the different components of it. You should be able to feel the magic in your chest where it mixes together with the air.”
Twilight sits down and closes her eyes, doing her best to follow Spike’s instructions, breathing in deeply and then slowly letting it out again. The first time there isn’t anything special to see, but Spike just stays silent and waits for her to continue. Soon enough, a breath releases as a slow, thin stream of purple flame that quickly dissipates as it leaves her muzzle. Twilight opens her eyes, staring down at the faint but hot stream of violet flame. “Amazing...” She murmurs, in some degree of awe.
Spike nods. “Now that you can feel it, you need to get it under control.” Spike hesitates. “I... Don’t know how to help you do that exactly, I don’t know how to explain it. It’s like tugging on a muscle in your chest, only its not really a muscle. But once you’ve gotten that under control, you need to get used to keeping it under wraps. Not only does that help keep you from letting out fire accidentally, but it helps keep enough of your magic together to breath fire if you need to.”
Twilight raises a brow. “If I need to? Why would I ever need to breath fire?” She asks, unconvinced.
Spike crosses his hooves in response, raising a brow right back at Twilight. “Oh? You’re telling me that dragonfire wouldn’t have come in handy when you fought Tirek, or Starlight?” He asks sarcastically. “Also works as a great sanitizer, if you don’t mind the smell of smoke. Sometimes I breath fire on myself, washes all sorts of stuff off. Comes in handy during barbecues, too.”
Twilight strokes her chin with her hoof. “Huh. I... Guess you have a point.” It is true that her little dragon assistant’s- No, little brother's- firebreath had come in handy from time to time. Even if it was more often just a hazard. But it seems like Spike has mostly gotten it under control, now.
Now she just needs to do the same. Which might be a bit of a challenge, given the vagueness of Spike’s directions. Shutting her eyes once more, Twilight focuses deep down, trying to feel the magic inside of her. Its an abundant reservoir, every bit as much a part of her as her flesh and blood. Maybe even moreso, because it had outlasted her original body.
But its nature has taken quite a beating over time, from her transformation into an Alicorn to the latest change now, and it is now almost entirely unrecognizable from the much simpler unicorn magic of yesteryear. All of the different types of magic within her combined to form an unusual, amorphous mixture of decidedly unknowable nature. If she had been a wild animal, Twilight would have been eager to study herself; well, no, even as she was, she was still eager to study herself.
But the first step in studying is making sure she can step foot in her laboratory without worrying about destroying her own research. So she takes hold of that magic within her, and clamps down on it, trying to expand her awareness of it. Just like Spike said, it feels more physical compared to using her unicorn magic, like controlling a muscle. Practicing, Twilight takes a deep breath in, and focuses on breathing out while damping her own magic. Though the specifics varied, its not fundamentally too different from keeping a handle on magic when reading spells to make sure she didn’t cast anything accidentally.
Spike grins, and claps his hooves together. “Good! You did it! Soon enough you’ll be able to say that you’re the best at dragon magic as well as every other kind!” Spike boasts.
Twilight blinks. “How did you know I did it? I mean, I could have just not breathed out enough to create fire.” She asks, curiously.
Spike shakes his head. “Nu-uh, ever since my transformation I’ve been learning to detect magic around me. I didn’t feel any of yours leave through your breath.
Twilight’s eyes widen. Detecting magical traces, especially at that minute of a quantity, is not an easy thing to do. Most unicorns never learned to do it; Twilight herself had only mastered the skill after she’d moved to ponyville.
Spike grins at Twilight widely. “Now comes the fun part. Point your muzzle up at the sky, then try and let ‘er rip! Its important to be able to control it in both directions to have full mastery of your breath.”
Twilight tilts her head back and takes in a deep breath, even deeper than any previously. Now, instead of clamping down on her magic, she pushes on it, widening the floodgates to release as much as she can. Inadvertently, some of the magic is released through her horn and wings, flares of purple flame jetting from her wingtips and the tip of her horn. She almost loses concentration in surprise, but keeps a hold on it just long enough to push her breath out all at once.
A brilliant, vibrant stream of purple fire arcs high into the air, far above the castle, so bright that the core of the flame appears closer to white and is blinding to look at. The heat pulses through the surroundings, as the flame separates into several forked tongues that dance into the sky almost with a will of their own.
Twilight staggers back and falls on her haunches, in apparent awe and exhaustion. “That's... Incredible! I haven’t felt a magical release like that since I absorbed the princesses magic to fight Tirek!” Twilight declares, elated. Her enthusiasm is cut short by the sound of distant screams.
“Dragon! Dragon! There’s a dragon in the castle!” Twilight can distantly hear pony voices shouting from town. Twilight covers her mouth, looking embarrassed, and looks over at Spike.
“Well... I guess we had better go explain the situation to everypony before there’s a panic, huh?” Spike asks, offering a hoof to Twilight, who nods quickly.
“Hopefully before the royal guard shows up.” Twilight replies, taking Spike’s hoof and teleporting away in a flash of violet fire.