Man Faces Nature
Dark magic is unnatural, unleashed through emotion and primal power. Defense is natural, defined by sacrifice and control. In the wide catalogue of defensive spells there are many kinds of magical shields, but the most powerful is the most personal – shielding with your body invokes the deepest magic.
Introduction to Confronting the Faceless, Chapter Three: Personal Defense in Theory and Practice
Quirrell's attack begins with the element of earth. Wandless and primal, his spell distorts the rigid strength of wood and soil, unbalancing the broom beneath Potter's hands. Its timber warps and bucks under the child, who quickly loses his seat. The broom's plunging handle swings back and forth in mid-air as the boy clings to it, his legs pin-wheeling uselessly beneath him.
Snape, sitting in the stands below, is taken by surprise – so much so that he doubts for a moment that Quirrell is behind this. Up to now, the stuttering fool has limited himself to crude stunts and diversions. It takes neither genius nor power to open the door to a rampaging troll, but it takes both to manipulate one of the essential elements. Only Dark magic of the most advanced kind can forge a weapon out of nature. Quirrell's hitherto unsuspected skill elevates his meddling to a new and disturbing level, but Snape has little chance to dwell on it. He fixes his eyes on Potter and braces his mind and body for defense.
Severus wraps his hands around the creaky wooden plank beneath him and whispers the counter-curse of elemental earth, feeling filaments of his magic blossom like ivy through his fingers, twining from his seat to the floor, down through the risers and out through the railings, branching all the way down to the stadium foundations. The immense, grounding power of earth and timber rises up into his palms, and he weighs Potter's quaking broomstick down with it. His incantation binds the broom to him like a ship to anchor, and he feels its erratic flailing in the flutter of his pulse. But it begins to calm almost at once, crushed under the dense magic he is absorbing through his hands.
Take that, you amateur, he thinks, and then all hell breaks loose.
Quirrell attacks with a second element, without loosening his hold on the first. This is unprecedented; it is insane. Without a wand, the only way to harness an element is to use your body as a temporary channel, and mixing warring elements within the body is spectacularly dangerous. But Severus can sense the moron doing it, reaching into the air with a burst of rage and stirring a whirlwind into motion around the boy, who is still dangling by one arm a hundred feet up. And instead of spontaneously combusting, as he should, Quirrell sits placidly in the stands with earth and air running through him, their fundamental opposition reduced to a meaningless trifle.
Severus realizes, in shock, that he's out of his league.
But he has to do something; the child is losing his hold in the screaming wind. He clenches his hands more tightly against his seat, forcing himself to remain painfully aware of wood and solid ground as he switches his incantation from elemental earth to elemental air. He has never done this before. The words bring an immediate rush of power, lightning and wild. It boils against the settled earth inside him, and the opposing forces react like magnets under his ribcage, pressing outward millimeter by millimeter, shifting his bones. He has the horrible sensation that his heart is being slowly shoved out of his chest. Tremendous power is coursing through him, but in order to wield that strength in defense, he must find some new way to offer his body as a shield.
He concentrates on the pull of his lungs, slowing his breathing and establishing a steady rhythm that rises and falls in tandem with his chanting. The painful pressure in his chest is distracting; one of his ribs begins to fracture. He gasps, upsetting his careful pacing, but has no time to refine his technique. He reaches out into the squall surrounding Potter and tries to regulate the storm with his own breaths; his counter-curse magnifies the calm air that is moving through him. It multiplies and mixes with the wild gusts; he feels them swirl in the back of his throat, and nearly gags. He forces his throat open and concentrates on inhaling and exhaling: once, twice, and again, and again. His eyes, still fixed and unblinking, begin to water as he feels new cracks spider along his ribcage, but he can see his spell start to take effect as Potter shakes himself free of the gale and tries to throw one leg back over his broom. He is not successful yet, but the tide is turning.
In utter disbelief, Severus recognizes a third assault gathering at the edge of his senses. A blast of hot air, as scalding as a furnace, begins to rise, and the element of fire adds itself to the day's impossibilities. But before he can even begin to formulate a response, it dissipates as suddenly as it appeared. At the same moment, the challenge of earth and air fade into nothing, the Dark spell breaks off – Quirrell abandons the field. Severus, confused and suspicious, releases his hold on air and earth but throws a furious litany of anti-inflammatory charms at the boy. He discovers he has misdirected them when he smells smoke thirty seconds later.
His concentration broken, he grabs for his wand and shoots a stream of water at the blue flames eating their way up his robes (that makes all four, he thinks angrily, thoroughly sick of primal elements). By the time he looks up, Potter has landed on solid ground and is busily hacking up the Snitch to universal applause.
The pain in his chest stabs quite intolerably.