Comment by tohu on Harry Potter and the Methods of Rationality discussion thread, February 2015, chapter 113 · 2015-02-28T20:38:03.396Z · LW · GW

Beneath the moonlight glints a tiny fragment of silver, a fraction of a line... (black robes, falling) ...blood spills out in litres, and someone screams a word.

I'm relatively confident that this quote is a part of the solution. Maybe Harry partially transfigures a monofilament blade and starts cutting down everything.