Harry Potter and the Methods of Rationality

Harry's hands tore open the healer's kit from his pouch, grabbed one of the self-tightening tourniquets, wrapped them around one ragged tooth-marked stump, his hands briefly slipping in the blood, they didn't tremble, there wasn't any allowance for his hands to tremble. As the tourniquet formed a complete loop it tightened hard and more blood came out, but then the bleeding stopped on that thigh-stump, and Harry turned to the other. Part of his mind was screaming, screaming, screaming and even the part of him picking up the other self-tightening tourniquet heard it, but that also wasn't allowed.

The two Weasley twins were shouting spells, one after another in rapid-fire casting that would have had Harry unconscious in sixty seconds, sometimes the twins shouted two spells simultaneously in perfect coordination, but most of the spells were disrupting in harmless showers of sparks against the troll's skin. As the other tourniquet tightened itself in another pulse of blood, Harry looked up at a "Diffindo!" / "Reducto!" that made the troll's vulnerable eyes explode in twin showers of vitreous humor, but the troll only bellowed once more, its eyes already reforming.

"Fire and acid!" Harry shouted. "Use fire or acid!"

"Fuego!" / "Incendio!" Harry heard, but he wasn't looking, he was reaching for the syringe of glowing orange liquid that was the oxygenating potion, pushing it into Hermione's neck at what Harry hoped was the carotid artery, to keep her brain alive even if her lungs or heart stopped, so long as her brain stayed intact everything else could be fixed, it had to be possible for magic to fix it, it had to be possible for magic to fix it, it had to be possible for magic to fix it, and Harry pushed the plunger of the syringe all the way down, creating a faint glow beneath the pale skin of her neck. Harry then pushed down on her chest, where her heart should be, hard compressions that he hoped was moving the oxygenated blood around to where it could reach her brain, even if her heart might have stopped beating, he hadn't actually thought to check her pulse.

Then Harry stared at the other things in his medical kit, his mind going blank as he tried to figure out what else of what was there, if anything, he could use. The screaming in that distant corner of his mind was getting louder, much louder, now that his hands had stopped their frantic motions. He was suddenly aware of the liquid sensation where blood had soaked through his robes and the knees of his pants.

From behind Harry came the sound of another bellow from the troll, and he heard one of the Weasley twins shout "Deligitor prodeas!" and then, "HELP! Do something!"

Harry twisted his head back to look, and saw that one of the Weasley twins was somehow now wearing the Sorting Hat on his head, facing off against the troll which held the huge stone club in both its hands, looking somewhat scorched now and with one or two smoking scars across its arms, but still intact.

And then the voice of the Hat bellowed in a voice so loud it seemed to shake the walls,

"GRYFFINDOR!"

A pulse of power burned the air, magic feeling almost tangible even to Harry's young senses, the troll jumped back a pace with a snort of surprise. Fred or George, with a strange look on his face, swept the Hat off his head with a motion smooth as a magician's trick, and reached in with one hand and drew forth a hilt whose pommel was a glowing ruby, followed by a wide crossguard of gleaming white metal, and a blade as long as a tall child. As the sword was revealed the air seemed to fill with a silent scream of fury.

Upon the blade was written in golden script, nihil supernum.

Then the Weasley twin raised the sword aloft as though the huge blade weighed nothing, and screamed and charged.

Harry's lips opened to say something, some long sentence like, No, stop, you have no idea how to use a sword but not even a single syllable left his lips before the sword sliced off the troll's right arm through the elbow, cutting through skin and flesh and bone like jelly; just as the already-swinging arc of the stone club smashed into the charging Weasley twin and sent him flying through the air above the marble floor, over the gap out of which they'd risen on the broomstick, until that Weasley hit the wall on the opposite side and then collapsed into an unmoving heap.

The bright sword vanished down into the opening in the floor, clattering distantly as it dropped.

"Fred!" screamed George Weasley, and then "VENTUS!"

An invisible blow caught the troll and hurled it sideways through the air.

"VENTUS!"

The troll was hit again, blown to the edge of the floor and the gap leading downwards.

"VENTUS!"

But the troll had reached down and grabbed at the floor, its remaining hand crunching through marble to gain a firm hold. The third blow sent the troll's body over the gap; but the hand remained at the edge. And then the troll was pulling itself back up single-handedly, roaring.

George Weasley staggered, almost falling, his hand dropping to his side. "Harry -" the Weasley twin said in a strained voice, "Run -"

The remaining Weasley twin took a step sideways, slumped against the wall, and slid to the ground.

Time was fractured in Harry's mind, the world around him seemed to move slowly, distorted, or perhaps it was his own mind twisting and folding. He should have been moving, doing something, but a strange paralysis seemed to be stopping all his muscles, all his motions. Without any time for words, thoughts came in flashes of concepts: that if Harry ran away the troll would eat the Weasley twins as well as Hermione, that if Bludgers didn't kill wizards then Fred should still be alive, that the Weasley twins were more powerful spellcasters than him and they hadn't been able to hold back the troll, there was no time to Transfigure anything he didn't already possess, the troll seemed too agile to be lured over the edge of the terrace to fall off the sides of the Hogwarts castle, someone had enchanted the troll against sunlight before using it as a murder weapon and might also have strengthened it in other ways. And then a mental image of Hermione running from the troll, running for sunlight, finally reaching the bright terrace with the troll hot on her heels, only to find that someone else had thought of that possibility, too.

The screaming horror in his mind was drowned out by another emotion.

Harry stood up.