An astropath is a sanctioned human telepath whose gift allows messages to be sent across the vast gulfs of the galaxy, forming the nervous system of the Imperium. Without them, the worlds of mankind would be isolated islands, unable to call for aid or coordinate defence across the immensity of space.
Every astropath has endured the Emperor's Soul Binding, a ritual conducted by the Adeptus Astra Telepathica that shields the mind against the predators of the Warp but leaves the recipient blind, their eyes burned away by contact with the Emperor's soul. In exchange they gain the strength to project thought across light-years, hurling telepathic sendings into the immaterium to be caught by distant kin.
The work is gruelling and perilous. Communication across such distances is imperfect, its meaning wrapped in symbol and vision that trained choristers must interpret, and the effort ages an astropath swiftly. Powerful sendings can kill, and the ever-present danger of the Warp means a careless psyker may draw the attention of things best left unnoticed. Yet these blind messengers remain irreplaceable, the silent voices that hold a scattered and beleaguered humanity together across the dark.