With the latest biological distraction out of the way, Sunburst threw himself back into his research. It was especially annoying when his stomach started acting up and he happened to be out of food, necessitating a supply run. He occasionally fantasized about magicing those needs away, but having even less magic than the average unicorn already made it a pipe dream, let alone him never finding a spell of the sort.
Back to the matter at hoof, he was working with a dark magic detection spell. The reason for this was that he found two versions of this: one that searches in a specific direction, and another that looks in all directions. After looking through the exact construction, he realized that the former was just the latter with a partial barrier erected just after the pulse is formed to block most of it, greatly increasing cost but improving utility in certain situations.
Feeling inspired, he started removing various components that weren't necessary, just there to provide convenience to a caster that can afford it. He stripped away things like distance calculations, strength analysis, visual feedback, and the like. Brought down to its bare skeleton, it was a spell that expanded in a shell and bounced back to the caster's horn where dark magic was found. Even better, he probably could cast that without much trouble, so long as he didn't try scanning the entire block. That cost increased by the square of the range, so he'll stick to his house at the maximum.
He charged his horn and carefully used the stripped-down spell construct he wrote in his notes, grinning when he felt the magic leave his horn in a pulse. The smile vanished when he felt an echo wash back weakly over his horn. He didn't remember how much range he gave it, so he quickly calculated the energy needed to cover his house and cast the spell again, getting a stronger echo back. Finally, he steadily decreased the power of the spell and recast it over and over again, stopping when he could just barely feel the echo and marking down that power level.
A part of him marveled at the success in severely reducing the drain of what was normally a high-level spell to the point where he could cast it so many times, but the rest wanted to know if he accidentally tore out a part that prevented a false positive from appearing. He walked to the middle of his kitchen, cast it at that last intensity, and... nothing.
It took half an hour of repositioning and varying the range before he was finally able to narrow down the source of the echo. It did give him a realization as to why there were so many moving parts, as the bare-minimum version of the spell didn't even give him a direction to look for, let alone size or distance.
He cast a final pulse with just enough power for that dark corner above the bookcase he was suspicious of, and grew more convinced when the echo returned. He pulled his reading stool from his desk and placed it in front of the shelves. He then stood on it with his hindlegs and braced his forelegs against the furniture to bring his eyes as far up as possible. It was enough for him to see a very panicked-looking arctic tern in there, which quickly flew straight for his face.
Sunburst flinched back, which was not the best idea, as he lost the support of the bookshelves and pushed his center of mass behind the stool. It was only a matter of time before he fell down hard on the floor with a groan.
After the pain subsided, he stood back up slowly. As far as he could tell, nothing was broken. He let out a final pulse of his stripped down dark magic detector spell, with just enough range to reach a little past where that bird was sitting and got no response. Either the bird or something it was carrying had a little dark magic infused, perhaps a remnant from King Sombra's curse. He shook off the slight headache indicating low mana reserves and started wandering through his home, contemplating how he could find it and study it.
Well, this was unlikely to work, but it didn't hurt to try. "I don't mean any harm," he said in a vague direction while sitting down at his dining table, as he was unsure where the tern was. "I just want to figure out why you're setting off my dark magic detection spell, and maybe try to cure you of it."
He sat there and waited for a while, and was just about to get up and formulate a new plan involving a net when the corrupted bird flew into the room and landed on the far side of the table. Sunburst was finally able to get a good look at it. Hopefully, the far darker coloration compared to other members of its species was the only symptom of the weak curse.
The bird was still eyeing him warily and looked poised to take off at any moment, so he added, "I'm not going to hurt you, I just want to help."
The wild creature that apparently can understand him to some degree relaxed a bit, but still seemed on edge.
"If it makes you feel better, and if you can even understand this, I promise that what I said is exactly what I plan on doing."
The bird seemed mollified, but still hopped off the table outside of Sunburst's line of sight. He got up from his stool to walk around the room so he could see it, but stood in place when he saw a flash of coppery fire.
Standing in the flesh in front of him was a sight he thought he'd only see in the newspapers, a changeling, prominent fangs shining slightly in the weak light.