E - Space E - Space ( also known as Exo - Space or Exo - Space - time continuum ) was a pocket universe existing alongside its prime universe of N - Space . It possessed an unusual greenish tint . ( TV : " Full Circle " , " State of Decay " ) Locations in E - Space had negative co - ordinates , where N - Space co - ordinates were positive . When the Doctor ' s TARDIS materialised on the planet Alzarius after it had travelled into E - space , the TARDIS scanner continued to show images of Gallifrey , which had the positive equivalent of Alzarius ' spatial co - ordinates . The scanner was made functional again by replacing its original N - Space image translator with one native to E - Space . ( TV : " Full Circle " ) The planets Alzarius , Terradon , ( TV : " Full Circle " ) the vampire planet , ( TV : " State of Decay " ) Ballustra , ( AUDIO : " The Invasion of E - Space " ) Shapeer , ( TV : " Warriors ' Gate " ) Isenfel , ( AUDIO : " Equilibrium " ) and Apollyon were all located within E - Space . ( AUDIO : " The Entropy Plague " ) Transit between the universes . The Fifth Doctor stated that the negative co - ordinates would make it very difficult for his TARDIS to travel there deliberately and not accidentally . ( TV : " Earthshock " ) By his seventh incarnation the Doctor was able to pilot his TARDIS between E - space and N - space , and was able to retrieve Romana II from the former . ( PROSE : " Blood Harvest " ) K9 was also retrieved . ( PROSE : " Lungbarrow " ) CVEs . Travel between N - Space and E - Space could occur via a Charged Vacuum Emboitment , or " CVE " . This was a hazardous and apparently random process , even using a TARDIS . ( TV : " Full Circle " ) The Logopolitan s created the CVEs which linked together the two universes as part of their plan to forestall the overdue entropic collapse of their universe , N - Space , by opening up what had previously been a closed system and thus dissipating the accumulated entropy . Following the disastrous consequences of the Master ' s visit to Logopolis , only one CVE remained open , in the constellation of Cassiopeia ( from Earth ' s perspective ) . ( TV : " Logopolis " ) Unless further CVEs were later created , it was highly likely this was the route through which the " Hydrax " would later enter E - Space ( TV : " State of Decay " ) in the 22nd century . ( PROSE : " Lucifer Rising " ) The Gateway . On his return journey to N - Space the Fourth Doctor and his companions passed through a strange white void known to its most frequent inhabitants , the Tharil s , as the Gateway . ( TV : " Warriors ' Gate " ) History . The Fourth Doctor , Romana II and K9 Mark II accidentally entered E - Space through a CVE . He landed on Alzarius where he met Adric , an inhabitant of the universe who secreted himself aboard the Doctor ' s TARDIS to join the Time Lord on his travels . ( TV : " Full Circle " , " State of Decay " ) They spent months trying to find another CVE . During this time , they encountered the Farrian , who had entered E - Space through a CVE . They had opened it themselves using Block Transfer Computation , a skill they learnt from a prisoner . The Farrian attempted to conquer the planet Ballustra , but the Doctor destroyed the device that generated the CVE , forcing them to retreat . ( AUDIO : " The Invasion of E - Space " ) The Doctor and Adric left E - Space through the Gateway . Romana and K9 chose to the stay behind . Romana did so to avoid a return to Gallifrey and K9 accompanied her . ( TV : " Warriors ' Gate " )