Rigelian

s were a humanoid species on good terms with the Time Lords. They got the loan of K9 from the Time Lords when the Rigelian Seventh Fleet disappeared. K9 liaised with a male Rigelian fleet commander, who sternly focused K9 on the task of discovering why the Seventh Fleet had been subjected to vanishment. (PROSE: K9 and the Time Trap)
 * Writer Dave Martin gave no other details about the species.