Over on FanFiction.net lies what is perhaps the best and most terrible (in what it has done to my brain) fic I have ever read, the great "Harry Potter and the Methods of Rationality" by Less Wrong [link]
And so, of course, I decided to pay tribute the only way I know how.
The story takes place in Harry's first year, but since I can't draw, I had to use the base pictures I could find, so they look a bit over eleven.
This picture, all three armies.
Also in the series:
Harry Potter's Chaos Legion [link]
Draco Malfoy's Dragon Army [link]
Hermione Granger's Sunshine Regiment [link]
All base images courtesy of the-leaky-cauldron.org