Fendahl The Fendahl were gestalt organisms from the original fifth planet of the Sol system . They were composed of two parts , a Fendahl core and the Fendahleen . The Fendahl posed a threat to all life , and when one Fendahl core and twelve Fendahleen coexisted they had the power to destroy all life on a planet . Biology . Thirteen physically separate organisms made up the Fendahl , twelve Fendahleen and the core . Additionally , a High Priestess of the Fendahleen would merge with them to complete the Fendahl creature . ( PROSE : " Doctor Who and the Image of the Fendahl " ) Fendahl core . The skull of the Fendahl core which transported itself to Earth resembled a human skull in every respect , but for a pentagram shape in the forehead , visible only by an x - ray . After her transformation into the Fendahl core in July 1977 , Thea Ransome appeared as a golden - skinned , majestic being with gigantic , unblinking eyes , long golden fingernails and an ornate ringed hairstyle . The core was practically invulnerable , not harmed by guns at all . When the skull was activated , it began to pulse with a golden glow from inside , and touching it caused great pain — apparently mental pain more than physical — although the cause of this was unclear . It could , however , be safely handled with gloves . ( TV : " Image of the Fendahl " ) Fendahleen . Each Fendahl core had twelve Fendahleen — eyeless and limbless creatures having a fringe of pink tentacles around their mouths , and two large fins above . Their weakness was salt , particularly when shot up their throat . It affected the conductivity , ruined the overall electrical balance and prevented control of the localised disruption of the osmotic pressures . In short , salt killed them , causing wisps of smoke to come out of their mouths . Surface contact with salt did not seem to have the same effect , but they did not seem to find it pleasant . When injured , Fendahleen squealed . ( TV : " Image of the Fendahl " ) Life cycle . Fendahls were psychevore s , meaning they fed on psychic energy . ( PROSE : " The Left - Handed Hummingbird " ) The Fendahl could drain all the spectrum of energy from their prey , effectively sucking out their souls . Even the skull nicknamed Eustace , the fossil remnants of a Fendahl core twelve million years dead , had the power to drain the life force of the Fourth Doctor . The core could create these Fendahleens from living beings with the correct genetic inheritance and in some cases could create the Fendahleen out of pure energy . If the core was destroyed , the Fendahl were killed . All of the parts of the Fendahl could telekinetically control people , but the core had many more psychic powers such as mind control and astral projection . ( TV : " Image of the Fendahl " ) History . Roughly 12 million years BC , the Fendahl evolved on the fifth planet , located between Mars and Jupiter . The Fendahl began to kill all life on the planet , including each other . When the Time Lord s learnt of the danger that the Fendahl posed , they placed the planet in a time loop . They also removed all trace of the Fendahl from their records , leading it to pass into legend . However , a Fendahl survived and was able to escape the planet in the form of a skull . ( TV : " Image of the Fendahl " ) In its travels it caused damage to Mars , leading to mass extinction . ( TV : " Image of the Fendahl " , PROSE : " GodEngine " ) It eventually came to Earth , arriving in Kenya . This skull was able to affect the development of humans in order to produce a species which it could use . ( TV : " Image of the Fendahl " ) The skull was eventually discovered by Dr Fendelman in the 1960s by discovering a " sonic shadow " and tracing it back to its source . He brought it back to Fetch Priory , which had a time scanner . The Fendahl was able to grow in power using the time scanner , killing several people and possessing Thea Ransome . A local coven , led by Maximillian Stael , believed they could control the Fendahl and tried to help it , but were instead turned into Fendahleen . The Fourth Doctor was able to stop the Fendahl by overloading the time scanner and removing the skull , planning to dump it in a supernova . ( TV : " Image of the Fendahl " ) This act , however , failed to destroy the Fendahl . Instead , it wound up causing another manifestation of the Fendahl on Kaldor City . ( AUDIO : " Checkmate " ) During the War with the Enemy , Time Lords from the Eighth Doctor ' s subjective future had planned to use a fleet of War TARDIS es to undo the time barrier s around Planet 5 in order to release the Fendahl , but it was discovered that the Fendahl had been killed when time inside the loop was accelerated , resulting in the last other life - form on Planet 5 evolving into the Memeovore , a devourer of concept that had evolved to kill the Fendahl itself . ( PROSE : " The Taking of Planet 5 " ) The Fendahl also was successful in duping Reynald , former Earl of Marseille , into summoning it in Jerusalem in 1098 , attracted to the destruction caused by the Crusades . It used a bone spear imbued with its life - draining properties to draw nourishment ( allowing it to be mistaken for the Lance of Longinus ) , allowing it to transform him into a Fendahl core and create several Fendahleen . However , due to the efforts of Simon , a knight of the period , Reynald was aged well into a decrepit state , weakening his ability to command the Fendahl ' s powers , killing both and banishing the Fendahl . ( PROSE : " Deus Le Volt " )