91-form timeships, also called the Ships of War, were created by the Great Houses during the years immediately before the War. Though not recognisably intelligent, the minimum-intensity biodata in their structures gave them a biological edge, suggesting they were aware of life on their pilots' level.
91-forms were also the first timeships designed to be indiscreet, appearing as consistently big, bulky, and unapologetic. In orbit, they were often mistaken for arks or flagships of lesser species; however, they more often rooted themselves on planets at ground level, pushing aside buildings and taking the forms of giant cathedral-like embassies for the Great Houses. Some such grounded 91-forms were incapacitated or abandoned and dug out of the group millions of years in the localised future, misidentified by the natives as relics of a lost civilisation or the bones of huge, semi-mechanical monsters.