The Knowhere was a torture computer, programmed to read the victim's mind and project its fears. The Fourth Doctor, Romana I, and Kimus were tortured by the Knowhere, with the following projections: a Dalek, drowning, sinking into sand, being alone in a dead TARDIS, and burning planets.
Romana I claimed her tutor would hate the Knowhere, whilst the Doctor claimed his would have "adored" it. (PROSE: The Pirate Planet)