Violet
Quite possibly they don't have a name, because it was proposed by some DE lackey instead of an actual Unspeakable. I hope people won't hold it against the Department of Mysteries once the dust settles, though. It's obvious they're under some kind of duress since no one ever sees or hears from them. Which, granted, has always been the nature of their department, but you'd at least bump into them in the break rooms sometimes.