Lysandra Aristedes Lysandra Aristedes , code - name Perseus while working for the Forge , was a companion of the Seventh Doctor . She inhabited the Black TARDIS , as did Sally Morgan . ( AUDIO : " Project : Nirvana " , " Black and White " ) Biography . She was born in 1982 . As a young child , her favourite television series was " Jimbo and the Jet - Set " . ( AUDIO : " Gods and Monsters " ) Working with the Forge . Lysandra was seconded to the Forge as a corporal , sometime between 2002 and 2004 . During this time she hunted down a lone grey alien in the New Forest , harvested a Slarvian at a peace conference , and investigated an alien prison ship which crashed in the Lapland s . ( PROSE : " Project Valhalla " ) Sometime before early 2008 , she was transferred to Internal Counter - Intelligence Service . While she was in ICIS , many of her colleagues at the Forge were killed when the Forge Alpha Facility was destroyed . ( AUDIO : " Project : Destiny " ) By 2015 , she was a sergeant . ( AUDIO : " Project : Nirvana " ) Lysandra stayed in London with Nimrod and Jarrod when it was evacuated due to the Forge accidentally released a contagious alien intelligence . The Seventh Doctor , Ace , and Hex landed in London at the time and met up with the Forge . Initially , Lysandra was very hostile towards the Doctor , blaming him for the deaths of her friends when the Alpha Facility was destroyed , telling Ace that he was ' corrupting ' her with his alien morality . However , when Lysandra realised that Nimrod had altered the Doctor ' s cure to the Contagion to kill all of the infected instead of curing them , she decided he was unfit to lead the Forge , simultaneously recognising that the Doctor was better than she believed as he had gone to great lengths to find a cure and was clearly outraged at what Nimrod had done . Activating the Destiny Protocol , Lysandra became the new director of the Forge under the authority of the Prime Minister . She decided that it would be too late to recreate the Doctor ' s original cure and ordered that the Royal Air Force destroy all of the infected with distronic missiles . ( AUDIO : " Project : Destiny " ) Travels with the Doctor . Three months later , Kai ' lizakia attempted to steal technology from the Forge by creating a cult known as the Sons of Kai . The Seventh Doctor and Sally Morgan came to London at this time and the Doctor had Sally infiltrate Lysandra ' s troop . When Lysandra ' s troop fought Kai ' lizakia , the Doctor became involved and killed the Elder God with a Cyber - Planner ' s cerebral cortex . Afterwards , the Doctor asked Lysandra if she wanted to travel with him . Lysandra said yes and she gave the Doctor the technology Kai ' lizakia had been trying to steal . ( AUDIO : " Black and White " ) The Doctor sent her and Sally on a mission to Romania in 2015 . She knew what the Doctor wanted but didn ' t tell Sally . She encountered her younger self , and discovered Nimrod had brainwashed her , so she couldn ' t be possessed by Derleth . Although , that didn ' t work and she had been possessed . However , Lysandra and Sally defeated Derleth . ( AUDIO : " Project : Nirvana " ) She travelled with Ace in the black TARDIS , whilst Hex and Sally travelled to 5th century Denmark to find the Doctor . Upon landing she started to explore she encountered Garundel who told her of how he met the Doctor . Garundel captured her but she escaped and tried to get the Doctor out of the regenerative pods . She discovered that he was looking for Weyland Shield , and she helped Garundel to survive decapitation . ( AUDIO : " Black and White " ) When the TARDIS was coloured blue again , she travelled with Ace , Hex , and Sally to the land of Fenric . She tried to kill Fenric , not knowing that he wouldn ' t be affected . She was placed in a time storm , flung into Sally ' s future , where she found that she was trapped by Sally ' s future platoon . Sally set the truth sayer on her . She knew the codes that would destroy the world via the Higgs Killer ; it was Nimrod ' s secret . She was rescued by Peggy Marsden . She tried to kill Fenric , but was attacked by the Haemovore ; her faith in the Forge saved her . When Hex was possessed by Fenric , she was the one to grant Hex ' s wish and opened the TARDIS ' s doors to for Hex o sacrifice himself . ( AUDIO : " Gods and Monsters " ) At some point , she taught Sally how to fly a helicopter . ( AUDIO : " Signs and Wonders " ) After this happened , the Doctor deposited Lysandra to fight in a war in the African States in her native time . ( AUDIO : " Afterlife " )