Spiridon Spiridon ( also known as Zaleria ) was the homeworld of the Spiridons . The planet was used for a base by the Dalek s in the early 26th century in their plan to destabilise the galactic balance of power before an invasion in force . Geography . Spiridon had an unusual geology . Its core was composed of friable ice , called " molten " . This would occasionally erupt onto the surface through fissures known as icecano es . Natural springs also brought it to the surface , forming molten ice pool s . The Plain of Stones absorbed heat during the day before releasing it at night . ( TV : " Planet of the Daleks " ) Indigenous lifeforms . Non - intelligent life . The planet was home to several non - intelligent predators , most of which were nocturnal . Many of the plants , like the eye plant s , also exhibited signs of sentience and were dangerous in their own right . One such species spat fungal spores at anything which came too close . The mould resulting from direct contact grew rapidly across the skin of anyone hit , rapidly incapacitating and eventually killing them . ( TV : " Planet of the Daleks " ) Intelligent life . The natives of the planet were known as Spiridons and were notable for being able to turn invisible . This was apparently an inherent characteristic , probably generated as part of essential life processes as it ceased to function " post - mortem . " When initially encountered by the Doctor , the Spiridons had been enslaved by the Daleks and so the nature and level of their native culture prior to this is unknown . It did not appear to be more sophisticated than a primitive tribal society . ( TV : " Planet of the Daleks " ) History . Spearhead of Dalek invasion force . Nothing is known of Spiridon prior to the Dalek invasion , which occurred at some time before 2540 . The Daleks established an extensive underground base near one of the icecano es and subjugated the local natives . The Daleks selected Spiridon as a base for at least two reasons . The icy core made it a promising location , given part of their plan involved building a massive army in sub - zero suspended animation ( although due to the erratic nature of the core , artificial refrigerator s were eventually used ) . The Daleks also wanted to study the invisibility of the native humanoid s , with the intent to replicating it for themselves . Experiments met with some success , although Daleks made invisible proved susceptible to light wave sickness . This incapacitated them . The Daleks on Spiridon were all said to have the power of invisibility , but only one was ever seen using it ( so to speak ) , and was discovered to have died from light wave sickness . ( TV : " Planet of the Daleks " ) The Daleks ' agent , the Master , had been successful at first in fermenting tensions between Earth and Draconia , but disaster came from an unexpected quarter when the location of the Dalek base became known to the Thal s . They dispatched several strike teams to stop the Dalek plan . The Thals were aided by the Third Doctor , who had learned of the Master ' s activities and been guided to Spiridon by the Time Lord s . ( TV : " Frontier in Space " ) The Daleks on Spiridon tried to exterminate their enemies by releasing a lethal biological weapon to sterilise the planet . Sabotage by a Spiridon native led to the weapon being released within the Dalek laboratory before the base could be immunised against it . The Doctor and the Thals used explosives to trigger an icecano eruption , burying the army of ten thousand Daleks in molten ice and ( they believed ) permanent deep freeze . The Dalek Supreme was stranded on Spiridon after the base was destroyed and its ship stolen by the departing Thals . ( TV : " Planet of the Daleks " ) Site of battle between Dalek factions . Some time later the Doctor brought Davros to Spiridon as part of his machinations to annihilate the Daleks permanently . Davros revived Daleks from the frozen army and changed their loyalties so they served him rather than the Dalek Emperor . A faction of Daleks loyal to the Dalek Emperor on Skaro , including a Special Weapons Dalek , came to Spiridon , led there by the Seventh Doctor , who was accompanied by Bernice Summerfield , Abslom Daak and the other members of the Star Tigers . The loyalists were defeated by Davros ' faction , with the almost - unnoticed assistance of a few Spiridon natives . Davros had apparently spent some time ( from his point of view ) on Spiridon preparing for the confrontation . Davros and his Daleks left Spiridon to begin their conquest of Skaro , taking the Doctor and his friends with them . The planet was left in apparent peace after this . ( COMIC : " Emperor of the Daleks " ) In the 42nd century , the Dalek s of the Seriphia Galaxy intended to awaken their lost army on this planet and recreate invisibility experiments for their conquest of Mutter ' s Spiral . The Seventh Doctor thwarted their plans and released the contagion that gave the Daleks a fatal light - wave sickness which Spiridons thought also killed the Doctor . The Dalek army was destroyed and invisibility was reclaimed to the natives of this planet . ( AUDIO : " Return of the Daleks " ) Dalek survivors . Spiridon was one of several planets where Daleks survived encounters with the Doctor . These survivors were classed as insane and taken to " intensive care " in the Dalek Asylum . The insane Daleks died when the asylum was destroyed by the Parliament of the Daleks . ( TV : " Asylum of the Daleks " )