"It's a Covenant charm. We use them here in the Department of Mysteries as a means of keeping secrets, well, a secret." The corner of his mouth tipped up in a smirk, his eyes alight with mischief. "As an Unspeakable, I could probably get in a ton of trouble for sharing this information, but I figure you're Minister now... You'll find out all the interdepartmental secrets sooner or later."