The Dune Encyclopedia, written by McNelly and 42 other contributors as a companion to the Dune series, was published in paperback in 1984. It describes in great detail many aspects of the Dune universe not covered in the novels themselves, such as character biographies and explanations of key elements, including planets, factions like the Bene Gesserit and Mentats, the spice melange, and technology such as heighliners and stillsuits.