Knowledge is deadly. Ten years ago, the Church was the leading light in Thean research. Now its natural philosophers are dead or in hiding, driven underground by the might of the Inquisition. But the flame of knowledge cannot be extinguished: the Invisible College carries on in secret, seeking to know the mind of Theus through the world he created. The Invisible College sourcebook details the secret cells of Theah's infant scientific community, a timeline of recent inventions and discoveries, and their ultimate goals.