Illuminati

In the fictional universe of Warhammer 40,000, the Illuminati are a subset of humanity, defined by having survived possession by a warp entity. Illuminati are special because their possession leaves them with a unique understanding of the warp and warp entities. Also, the Illuminati are among the few allowed to enter the Black Library (Illuminati, Inquisitors of the Ordo Malleus, Solitaires).