SORDIDE Delta

 was space station which was a research centre. It contained Shadow-Space which they were experimenting on but ended up being used as recuperation for those infected by a disease. The Maschera invaded it as revenge for what the humans did to their worlds. The Fifth Doctor, Nyssa and Hannah Bartholemew once visited it, and Hannah stayed behind after her rescuing the crew but she was left in a robot-like state. (AUDIO: Masquerade)