Styggron Chief Scientist Styggron was a Kraal who devised a plan to invade Earth , allowing his species to leave their native Oseidon where radiation was reaching hazardous levels . Marshall Chedaki served him in this . For this scheme , he created the Kraal android s . Using a pattern analyser , the memory and intelligence of any living being could be fed into an android that then assumed the appearance of the subject . Styggron brainwashed Guy Crayford , having him believe that the scientist had saved his life and that the Kraals wished to peacefully co - exist with the humans . On Oseidon , he created a replica of the English village Devesham and populated it with androids . This served as a training ground in preparation for the invasion of Earth and the conquests Styggron hoped would follow . He had Crayford , who had no android duplicate , take charge of the Space Defence Station , which was also copied . When the Fourth Doctor and Sarah Jane Smith came to Oseidon , landing in the replicated Devesham , he ordered that they be taken prisoner , countermanding Crayford , who wanted them killed . He had Sarah analysed and a reproduction of her created . Styggron also built a duplicate of Crayford that would recognise Kraals as hostile . He destroyed it to display to Chedaki the power of a handheld weapon he had developed , which he hoped would be adapted for use on Kraal space cruiser s . The Doctor was taken prisoner and Styggron had him tied up in the centre of Devesham and a matter dissolving bomb planted by him . The bomb detonated , destroying the testing ground , but the Doctor was freed by Sarah before he was killed . Styggron had developed a virus which would wipe out humanity in three weeks , allowing the Kraals to benefit fully from the Earth ' s limited resources . The Doctor and Sarah were recaptured with the Time Lord , at Crayford ' s insistence , being subjected to analysis . Styggron did so in the knowledge that the Doctor will be killed by the process . He also had food and water laced with the virus sent to Sarah , hoping to examine its effects upon her as previous tests had not been carried out on living subjects . Styggron boarded Crayford ' s XK - 5 space freighter which set off for Earth . The Doctor was on board , having been freed by Sarah who was with him . A number of the personnel at Devesham Control were already replaced by androids when the Doctor arrived , and a duplicate of the Doctor was introduced . The Doctor was able to use the radar dish es to disable the androids and free the real Harry Sullivan and Colonel Faraday . Styggron confronted Sarah , questioning her on how she survived , but Crayford , who had discovered that he had been lied to , attacked the Kraal . Styggron shot and killed him but was then attacked by the android duplicate of the Doctor . It had been reprogrammed by the Time Lord and , in knocking him down , caused him to fall on the container in which the virus was being kept . As it killed him , he shot at the android , destroying it , but died without knowing that it wasn ' t the real Doctor . ( TV : " The Android Invasion " ) He was succeeded as Chief Scientist of all the Kraals by Tyngworg . ( AUDIO : " The Oseidon Adventure " )