Harry Potter and the Methods of Rationality

'I didn't!' said Kellah.

'Yes you did!' shrieked Cesi. 'General Malfoy, she's the spy, I should've rea-'

'Somnium,' said Draco.

There was the triple bell of a one-point loss from Dragon, and then Kellah's limp body began to float away in the water.

Draco had heard the word 'recursion' by this point, and he knew a Harry Potter plot when he saw one.

(Unfortunately Draco had not heard of autoimmune disorders, and the thought did not readily occur to him that a clever virus would begin its attack by creating symptoms of an autoimmune disorder so as to get the body to distrust its own immune system...)

'General order!' said Draco, raising his voice. 'Nobody gets to shoot spies except myself, Gregory, Padma, and Terry. If anyone sees anything suspicious they come to one of us.'

And then -

There was the bell of Sunshine scoring two points.

'What?' said Draco and Zabini around the same time; their heads swiveled around. No one seemed to have gotten hit, and all the Sunshine soldiers were present and accounted for. (Except Parvati, who had been shot by some still-unknown traitor in Padma's squad; and of course Padma had shot Parvati again in case she was faking, so it wasn't her...)

'A Sunny traitor in Chaos?' said Zabini, sounding puzzled. 'But all the ones I knew about were supposed to strike during Chaos's attack on Sunshine -'

'No!' said Padma in a tone of sudden realization. 'That was Chaos executing a spy!'

'What?' said Zabini. 'But why -'

And Draco got it. Damn it! 'Because Potter thinks he's safe for how much he beats Sunshine, but not for how much he beats us! So he doesn't want to lose a single point when he executes a traitor! General order! If you have to execute a traitor, call Sunshine first! And don't forget to switch back to Dragon afterward -'

Granger: 253 / Malfoy: 252 / Potter: 252

Longbottom's body drifted chaotically through the water, arms and legs disarrayed. After Draco had finally got a hit in they'd all shot him again just to be sure.

Nearby was Harry Potter, now protected by a Prismatic Sphere, looking at them all grimly as the last sliver of crescent moon slowly diminished, somewhere far away. If Longbottom had managed to shoot one more soldier (Draco knew Harry was thinking), if the two Chaotics had managed to hold out just a little longer, they might have won...

After Draco had reformed his forces and struck out again, the ensuing battle and execution of spies in Sunshine's name had left Sunshine exactly one point ahead of Dragon and Chaos both. Once Harry had started doing it, Draco had been left with no choice but to follow suit.

But now they had General Chaos outnumbered three to one, the survivors of Dragon Army and the last remaining Sunny traitor: Draco, and Padma, and Zabini.

And Draco, who was no fool, had ordered Padma to take Zabini's wand after Longbottom had shot Gregory and fallen in turn to Draco. The boy had given him an insulted look, told Draco that he owed him for this, and handed it over.

That left Draco and Padma to take down General Chaos.

'I don't suppose you'd like to surrender?' said Draco, smiling as evilly as any smile he'd ever directed at Harry Potter.

'Sleep before surrender!' shouted General Chaos.

'Just so you know,' said Draco, 'Zabini doesn't actually have an older sister for you to rescue from Gryffindor bullies. But Zabini does have a mother who doesn't approve of Muggleborns like Granger, and I wrote her a few notes, and offered Zabini a few favors - nothing involving my father, just things I can do in school. And by the way, Zabini's mother doesn't approve of the Boy-Who-Lived, either. Just in case you still thought Zabini was really on your side.'

Harry's face grew even grimmer.

Draco raised his wand, and began breathing rhythmically, building up strength for a Breaking Drill Hex. Granger's Prismatic Sphere was almost as strong as Draco's now, and Harry's wasn't much weaker, where did those two find time?

'Lagann!' spoke Draco, putting everything he had into it, and the green spiral blazed out and Harry's shield shattered, and at almost the same moment -

'Somnium!' said Padma.

Granger: 253 / Malfoy: 252 / Potter: 254

Harry let out a long breath of relief, and not just because he didn't have to hold the Prismatic Sphere any more. His hand was shaking as he lowered his wand.

'You know,' said Harry, 'I was pretty worried there for a moment.'

Special Order Two: If a Sunny traitor doesn't seem to be really shooting at you, fake being hit occasionally. Prefer targeting Dragons to Sunnies but go ahead and shoot Sunnies if you can't shoot Dragons.

Special Order Three: Merlin says do not shoot at Blaise Zabini or either Patil twin.