The Kustollons were a race from the planet Kustollia. They used biotechnology for their spaceships and could also grow artificial telepathic lifeforms out of raw genestuff. The Ninth Doctor believed them to have "big noble aims in the long term" and "disastrous [aims] in the short".
In 3046, the Kustollons fought the humans of Earth in an "enormous, terrible battle" over disputed territories in the Perseus arm. The humans won using a virus developed from Peter and Charlotte Cobb's research which disabled the Kustollons' biotechnology. The Kustollons' already-ailing empire collapsed and "never truly recovered"; its government growing more militaristic and xenophobic. The scientists, including Igrix and his allies, planned to send a prototype time machine back to 1966 Earth to change history and prevent humanity from ever going out into space. This plan was thwarted by the Ninth Doctor using a virus adapted from Peter and Charlotte Cobb's research that had beat the Kustollons' organic weapons in the 31st century. (COMIC: The Love Invasion)