Crouch, Nott, or Jugson, though I'd guess the latter more heavily -- Jugson's constantly in the center of the blood-purist aligned factions during one of the battle games, and mentioned as Dumbledore's example of a powerful Death Eater with a seat on the Wizengamot, as well.
Mr. White was selected for a particularly humiliating and harmful process, and coincidentally Quirrelmort had wanted to harm Lucius badly on the scale of framing him for attempted murder of his own son, and there's a pretty clear connection.
Ironic that the canon Wikia says that it's not even known whether Jugson was free or an Azkaban escapee! Eliezer has certainly made him a much more significant character.
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 120.
Plans for next chapter release:
There is a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)