Kroton ( species ) The Krotons were a crystalline race from the planet Krosi - Aspai - Core . Biology . The Krotons evolved from predatory quasi - organic tellurium based crystal which could mimic their prey ' s abilities . At some point in their history they encountered a human servo robot and mimicked it , thus attaining semi - sapience . As they evolved they became semi - sentient armoured crystalline beings which fed on and were psychologically linked to mental vibrations . The Krotons had crystalline bodies which could be broken down and reformed to suit the environment and the situation which they were in . ( PROSE : " Alien Bodies " ) Krotons had poor eyesight in daylight and kept the insides of their ships dark . When venturing out in the daylight , a Kroton had to rely on the guidance of another Kroton giving directions through use of a mobile camera . ( TV : " The Krotons " ) Krotons of the Kroton Imperium could alter their bodies into a " combat - shape configuration " . More powerful than those the Doctor was familiar with , these Krotons could easily destroy a party of Quark s . ( COMIC : " The Lost Dimension " ) History . According to the Fourth Doctor , the Krotons inhabited a completely different era and region of the universe to the Quark s . Thus , to witness a conflict between the two races would not " make sense " . ( COMIC : " The Lost Dimension " ) Early history . The Kroton Absolute were overseen by the First Lattice , originally a fortress on the Kroton ' s home world . It contained the four highest brains in the Kroton Absolute . The First Lattice was moved from the Kroton home world when the war began with the Metatraxi . It took over four thousand Krotons to lift the First Lattice into orbit and it had exhausted all of them . ( PROSE : " Alien Bodies " ) Encounters with the Doctor . The Krotons encountered the Doctor on at least three occasions . On one occasion the Second Doctor killed a pair of Krotons stuck on a planet of Humanoid slaves known as Gond s . The Krotons had enslaved and manipulated the lives of the Gonds for generations so that they might power a dynatrope ( a Kroton spacecraft ) with mental energy and escape the planet . The Doctor assisted in the Krotons ' destruction with sulphuric acid . ( TV : " The Krotons " ) In his sixth incarnation , the Doctor found a dynatrope on Onyakis with what appeared to be an army of Krotons on board , which had been discovered and reactivated by a group of human s looking for a new source of energy for their colonisation ships . Rather than allow the humans on board the ship to be turned into batteries , the Doctor instead induced a temporary state of hypoxia on the humans already being used , the unstable mental patterns caused by it causing the Krotons to be obliterated by their own equipment . ( AUDIO : " Return of the Krotons " ) The third encounter was on Earth during the auction of the Relic . The Kroton Absolute intercepted a Dalek cruiser on its way to the auction and sent a Kroton of the Dalek s ' ship in their place . The eighth incarnation of the Doctor , who attended the auction , was unaware at first of the Relic ' s origins or of the Krotons ' presence . ( PROSE : " Alien Bodies " ) By the 29th century , the Krotons became part of the gestalt that was the Ixtricite , along with other crystalline races . ( PROSE : " The Fall of Yquatine " ) When Pericles Torp was a baby , the Krotons invaded Christmas , attempting to assassinate the Eleventh Doctor to prevent another Great Time War . During the attack , the Krotons destroyed a grain warehouse and several of the villagers hiding inside were killed . The Krotons were eventually defeated by the Doctor , but the loss of life stood as a reminder for the townspeople that he could not save everyone . ( PROSE : " The Dreaming " ) Alternate universes . In an alternate universe , the Krotons , organised into the Kroton Imperium , were the dominant power of their reality , theorised by the Fourth Doctor to be the result of a hypothetical absence of the Dalek s . A fleet passed into a gate through the Void to N - Space and engaged in battle with alternate Quark s who had arrived the same way . Discovering the Doctor ' s TARDIS , they engaged a transmat opposing that of the Quarks to bring it aboard , with the Fourth Doctor and Romana II taking the chance and boarding one ship , which they found inhabited by advanced Krotons , to stop the tug of war . A boarding party of Quarks was transmated to the ship to intercept but was quickly destroyed by the Krotons . Soon after , both Kroton and Quark fleets were attacked by forces of the Ogron Confederation of Planets who , coming from yet another universe , sought to cease hostilities between what they saw as " lesser - evolved species " via the use of deadly force . Ultimately , all three sides retreated to face a crisis in their respective universes . ( COMIC : " The Lost Dimension " ) Other references . When the telepathic Emily Fairfax read the mind of the Hypothetical Gentleman , a Kroton was among the images she saw . ( COMIC : " Hypothetical Gentleman " ) During the Eleventh Doctor ' s stay on Trenzalore , he would tell stories of his encounters with the Krotons to the townspeople of Christmas , possibly implying that the Krotons were at Trenzalore as well . ( PROSE : " An Apple a Day . . . " )