Werdeth pushed the bathroom door opened and noted with relief that nobody was inside. What had been a faint twinge in his shoulderblade was now a burning pain, centered there but spreading through most of his chest and up across the back of his head. It wasn't natural; whatever it was, someone had done this to him.
Ignoring the pain by an act of will, he crossed to the rearmost stall and closed the door. Inside, he unbuttoned his shirt and pulled it off, then hung it on the back of the door. His flesh looked normal, but he thought he could feel a faint tingling when he held his fingers above the center of the pain. He needed to get this under control, before something bad happened.
It wasn't a physical problem, so it had to be sorcery. Miserable as it was, it probably wasn't an attempt on his life; something like that would have been either much faster, or much more subtle... unless his peculiar talent was reacting unexpectedly, of course. That meant one of the other students, either aggravated by his arrival, or just being cruel for the pleasure of it. It might even have been some sort of test; they might have expected him to catch it and counter it before it became debilitating. His talent didn't work that way, but the other students didn't know that.
His left hand folded into a fist, claws digging into his palm. That was bad; he wasn't supposed to have claws. That entire arm was covered in dark fur, now. He forced the change back, refusing to let the pain distract him. Then, cautiously, he started to shift, looking to become something that could handle the pain. His skin hardened into armor plates, grew clusters of spikes, began to drip something that sizzled when it hit the tile floor...
He forced it back, again. That wouldn't work. He only knew one mode well enough to assume it safely; anything else meant letting the beast find its own way. If the beast took control with this sort of goad, it might very well kill, or be killed, or both.
For a moment he just stood there, breathing hard, willing his body to obey. When he had control again, however tenuous, he straightened. This magic, this spell, this curse... whatever it was, it was in his body now; it was part of him. He twisted it, shaped it, tore it loose from his flesh. It sat on his forearm, glaring, claws digging at skin that grown hard as bone: a nasty little thing, misshapen, with tiny eyes in a head that was almost entirely teeth.
He met its eyes, still exerting control. "Back," he said quietly, and it flinched away. He made a casting gesture, and it leapt from his arm. He opened the stall in time to see it slither under the bathroom door and out into the hall. It was going back to whomever had created it, wherever they were. Probably in class, he decided, and reached for his shirt. It was time to head back to his own classroom, preferably before the little beast found its creator.