The Arce Secretorum is a top-secret Inquisitorial facility devoted to the secure storage and study of powerful Chaos Artifacts, Daemonic Apocrypha, and other Warp-related arcana. Created by the newborn Ordo Malleus in the years following the end of the Horus Heresy, the Arce has served the Imperium's Daemonhunters well for millennia, for the contents of it's vaults and libraries has provided many an important insight into combating the Ruinous Powers. However, those same contents are extremely dangerous, and if even a few of the relics from it's vaults were to fall into the wrong hands the results would be catastrophic, thus the existence of the Arce Secretorum is known to a precious few.