Black Easter is a fantasy novel by American writer James Blish, in which an arms dealer hires a black magician to unleash all the demons of Hell on Earth for a single day. It was first published in 1968. The sequel is The Day After Judgment. Together, those two novellas form the third part of the thematic After Such Knowledge trilogy (the title is from a line of T. S. Eliot's Gerontion: "After such knowledge, what forgiveness?") with A Case of Conscience and Doctor Mirabilis. Blish has stated that it was only after completing Black Easter that he realized that the works formed a trilogy. A shorter version of Black Easter was serialized as Faust Aleph-Null in If magazine, August–October 1967; the book edition retains the phrase as its subtitle. Black Easter and its sequel were later published as a single volume under the title Black Easter and The Day After Judgement (1980); a 1990 edition from Baen Books was renamed The Devil's Day. Background Black Easter and The Day After Judgment deal with what sorcery would be like if it existed, and the ritual magic for summoning demons as described in grimoires actually worked. Its background was based closely on the writings of practicing magicians working in the Christian tradition from the 13th to the 18th centuries. Plot summary In the first book, a wealthy arms manufacturer, Dr. Baines, comes to a black magician, Theron Ware. Initially Baines tests Ware's credentials by asking for two people to be killed, first the Governor of California, Rogan (Reagan was governor at the time of writing) and then a rival physicist. When this is accomplished to Baines' satisfaction, Baines reveals his real reason: he wishes to release all the demons from Hell on Earth for one night to see what might happen. The book includes a lengthy description of the summoning ritual and a detailed (and as accurate as possible, given the available literature) description of the grotesque figures of the demons as they appear. Tension between white magicians (who appear to have a line of communications with the unfallen host in Heaven) and Ware is woven over the terms and conditions of a magical covenant that is designed to provide for observers and limitations. Black Easter ends with Baphomet announcing to the participants that the demons can not be compelled to return to Hell: the war is over and God is