The Veilbreaker Sigil — also called Mirror's Medallion in the older accounts that bothered to record both names — is a celestial-grade artefact whose work is small, precise, and rarely needed. It reveals deception. Where a thing has been disguised, it shows the disguise. Where a name has been borrowed, it shows the borrower. Where a body is being driven by something that is not its own will, it shows the hand on the controls.
Its limits are strict. It has charges. The charges, when spent, leave the artefact dark for a long count of days before the celestial weight in it can be drawn on again. It cannot be wielded carelessly. It cannot be wielded by anyone who does not already know roughly what they intend to look at — the Sigil shows truth, but it does not interpret it, and the truth it shows in untrained hands has a long history of being dismissed by the people who needed it most.
It is still kept behind glass, somewhere in the higher orders of Celesterra's few remaining faithful institutions. Its location is not written down in any place a stranger could find. The Sigil has not, in any account that has reached the chronicle, yet been turned on Drexel. The chronicle has begun, in this season, to suspect that day is approaching.