Voldemort had tried to show off his skills, only to trip himself up. Dumbledore certainly would not let such a perfect opportunity slip away.
The instant the Stone Serpent coiled around Voldemort, Dumbledore swept his left hand, and an enormous mass of earth and stone surged toward Voldemort, enclosing him in a sphere in the blink of an eye.
Dumbledore flicked his wand upward. The sphere rose into the air as more earth and stone gathered around it. In the space of a breath, the stone sphere expanded from a mere two meters in diameter to roughly five.
Dumbledore quickly uttered a spell. A sheen of light flashed across the surface of the sphere of earth and stone, and the next moment, it crystallized into an enormous black sphere.
Obsidian?
Tris felt dizzy at the sight.
He had long known that Dumbledore was the greatest wizard of their age and its most accomplished practitioner of Transfiguration, but actually seeing him in action still exceeded his expectations.
Transfiguration could change the properties of matter for a certain period of time. Transforming inanimate objects was one of its fundamentals, something even first-year students could do. In their very first Transfiguration lesson, Tris, Harry, and their classmates had learned to turn matches into needles.
Turning a wooden match into steel was not particularly difficult. At least, everyone in Tris's year could do it by now; the only difference was how long their magic lasted.
But some changes to an object's properties were harder than others.
Transfiguration could also produce gold, but unlike the Philosopher's Stone, which completely altered the properties of matter to turn stone into gold, its effects were temporary. Yet even with that time limit, this kind of Transfiguration was extremely difficult.
The reason lay in the magic resistance of materials.