Dalek Sec Dalek Sec was the leader of the Cult of Skaro , and later , a Human - Dalek hybrid . Known for being given the capability to think beyond the normal scope of a conventional Dalek , he eventually resorted to unorthodox methods to keep the Dalek species alive . The act that ultimately doomed him was tampering with the genetic template of his species , which was considered an affront to the existence of pure Daleks , and repulsed the other Daleks under his command when he chose to undergo an evolution into a new form . His personality vastly changed following his transformation , going from a ruthless strategist to a pacifist , and his subordinates responded accordingly by going from following his orders unquestioningly to rebelling against him . Biography . Origins . Dalek Sec was the commander of the Seventh Incursion Squad whose mission was to wipe out the Mechonoid s . Sec commanded from on the battlefield overseeing the field from vantage points . After the Mechonoids were exterminated , Sec returned as ordered to the Emperor . Sec was selected as the leader of the Cult and given his name . He was then sent to the weapons research area for upgrades , where he was re - encased in Metalert , a type of Dalekanium that was defensively superior to standard Dalekanium . Sec , along with the rest of the Cult , began using their initiative to defeat enemies . ( PROSE : " Birth of a Legend " ) During the Last Great Time War , they managed to escape the carnage by hiding between realities in a Void ship . ( TV : " Doomsday " ) The Battle of Canary Wharf . Emerging from the Void Ship along with the Genesis Ark , a Time Lord device , Sec served as Dalek commander during the Battle of Canary Wharf against the Cybermen . He and the other Daleks seemed unfazed by the Cybermen ' s invasion , stating , " This is not war — this is pest control ! " Sec led the Daleks to the top floor of Torchwood Tower , where the Cult of Skaro opened the roof and ascended to a space where the Genesis Ark could open . Sec and the rest of the Cult of Skaro released an army of Daleks from the Genesis Ark , which started to fight the humans and the Cybermen present at the battle and in the streets below . The Tenth Doctor was able to open the void which caused the Daleks , the Cybermen and everything else which had travelled through the void to be pulled into it . Instead , Sec and the Cult initiated an emergency temporal shift and vanished before they were sucked into the void . ( TV : " Doomsday " ) 1930s New York . Sec , along with the Cult of Skaro , ended up in New York City in 1930 and established a base beneath the Empire State Building . The Cult of Skaro attempted to create new Dalek mutants and revive the Dalek race ; when those attempts failed , Sec decided to attempt the " Final Experiment " : blending Dalek with human . He enveloped Mr Diagoras and began to " evolve " . ( TV : " Daleks in Manhattan " ) Human hybrid . While in his new body , he began to feel humanity for the first time in his existence . Motivated by emotions beyond anger and hate , and rejecting the traditional Dalek drive to conquer , Sec asked the Doctor to help him create more hybrids using mindless human bodies . Sec started to express his feelings that their creator had been wrong . He decided to create the new race of Dalek humans , different from the Daleks , out of the belief that if they continued to try to be superior , they would eventually die . However , the other Daleks came to reject Sec ' s theories as heresy , and eventually betrayed him . Dalek Caan took control and fuelled the other human bodies with pure Dalek DNA , in place of Sec ' s distinct mixture of the two . When the new Daleks in human shape tracked the Doctor down , they took Sec with them , putting him in chains . Taken before the Doctor , Dalek Thay accidentally exterminated Sec when he stood between Thay and the Doctor , either intending to save the Doctor by sacrificing himself , or expecting Dalek Thay to obey him and stop the mutiny . The Doctor openly declared his great respect for Sec , calling him the " cleverest Dalek ever " and the only creature that could have led the Daleks from the darkness . Dalek Sec made a prediction mere seconds before his death , stating , " My Daleks . . . understand this . If you choose death and destruction . . . then death and destruction will choose you . " Dalek Jast dismissed the thought at the time , but a minute later he was the next of the Cult to die , at the hands of the Dalek - human hybrids . Dalek Thay was killed shortly thereafter , leaving only Caan , who performed an emergency temporal shift and disappeared . ( TV : " Evolution of the Daleks " ) Personality . As leader of the Cult of Skaro , Dalek Sec was more intelligent and creative than most Daleks ; indeed the Doctor thought that he was the cleverest Dalek to have ever existed . Nevertheless , before his transformation , Sec was just as vicious as any other Dalek , mercilessly shooting down anyone who got in his way during the Battle of Canary Wharf . ( TV : " Doomsday " ) Although he displayed no mercy to his enemies , Sec was willing to sacrifice himself for the good of his race and believed that he was doing so by going through the " final experiment " . After using Mr Diagoras to transform into a human Dalek , Sec ' s personality changed and he began to feel compassion and mercy , feelings that the Daleks had been incapable of for thousands of years . He told the Doctor that the deaths the Daleks had caused were wrong and that their creator was also wrong to make the Daleks the way they were . He also displayed respect for humanity and commented that , despite their faults , they possessed courage . Sec was very dedicated to the Daleks but also felt that " purity " had brought their race to near - extinction . He believed that the Daleks had to change and adapt to survive . He hadn ' t intended for his transformation to result in him gaining human emotions , but believed that these emotions were good and that if the Daleks accepted them , they would survive . Unfortunately his Dalek companions disagreed with him and this eventually resulted in them betraying him . Sec tried to reason with the other Daleks either by demanding that they obey him due to him being their leader or begging them to listen to him . Sec eventually sacrificed himself to save the Doctor , showing that he had become a much better person than he had been as a " pure " Dalek . ( TV : " Evolution of the Daleks " ) Other information . Dalek Sec , as with all Daleks that originated from the Last Great Time War , possessed markings below his eyepiece to identify him . ( TV : " Doomsday " ) Behind the scenes . " The Visual Dictionary " . The source " " gave further information about the Dalek Sec . His human emotions are caused from merging with Diagoras ' ( obviously ) human brain . His six tentacles ( three either side of his face ) are from merging . He gained dexterous fingers , and due to more - exposed - than - human flesh , this makes him weaker to attack . After fully merging and leaving the Dalek , its casing , along with the weapons , were gotten rid of as they no longer served any purpose .