Shadow Kin The Shadow Kin were a race of fire - type humanoid s that could only survive physically with the presence of a shadow . They were led by the Shadow King , Corakinus and very briefly by April MacLean . Corakinus described his kind as " an accident " , saying they should never have been born into a universe of light . ( TV : " Co - Owner of a Lonely Heart " ) As April MacLean explained , the Shadow Kin believed that they were an evolution ary mistake , " like a peek into the universe ' s dark side that it never wanted " , and so they were " cast down [ into the Underneath ] to live in [ the universe ' s ] shadows and be forgotten . " This was a major drive behind their invasions . They also believed that the universe would crush them if they didn ' t defeat it . April called this a part of their religion . ( TV : " Co - Owner of a Lonely Heart " ) Biology . The Shadow Kin could exist as " pure shadow " , living unnoticed and untouchable in other people ' s shadows . In that form , they could only be killed if the person casting this shadow was killed as well . They could take on a solid form as well to kill their victims by surprise . Even in their most solid form , they could not exist when there were no shadows . ( TV : " For Tonight We Might Die " ) Shadow Kin were capable of producing scimitars as weapons from their own bodies . ( TV : " For Tonight We Might Die " , " Co - Owner of a Lonely Heart " ) History . The Shadow Kin emerged on the planet Rhodia amidst a war between the Rhodian s and the Quill . Taking the native population of three billion off guard , the Shadow Kin drove them to near extinction with the exception of the Rhodian prince Charlie and a single Quill forced to serve as his protector as a punishment , who were relocated to Earth by the Twelfth Doctor . Tracking the fugitives to Coal Hill Academy , the Shadow Kin , led by Corakinus , emerged through a tear in space - time at the school ' s prom night where they proceeded to mercilessly hunt for the pair before they were ultimately confronted by the Doctor , who Miss Quill had summoned for help . When the Doctor used the Shadow Kin ' s aversion to light against them , Corakinus and his kind were forced back through the tear from where they came which the Doctor subsequently sealed , though not entirely . Corakinus warned , however , that the Shadow Kin would return . ( TV : " For Tonight We Might Die " ) After Kharrus helped create a link to April on Earth using an anchor of a life blood , Corakinus planned to send his army to attack Earth . ( TV : " Co - Owner of a Lonely Heart " ) When April found her way to the Shadow Palace in the Underneath and defeated Corakinus in battle , she became the new king , and had the Shadow Kin lock up Corakinus . She ordered them to kill the killer petal s in Shoreditch on Earth , and had them close the crack that brought them through on the way back to the Underneath . ( TV : " Brave - ish Heart " ) They later returned back under Corakinus ' command , and they use other smaller tears to enter back to Earth . Corakinus revealed his intent to take April back to the Underneath with him , so he could have her heart in his body forever . When Charlie was posed with an tough decision , April read Corakinus ' thoughts and realised that the Shadow Kin were planning to wipe the human race out regardless of whether she went with them or not . Charlie decided to use a displacement gun to kill April and Corakinus , thus allowing Charlie to become the new King . He ordered his army to retreat , and then he used the Cabinet of Souls to wipe them out . After he used the cabinet , April resurrected but in Corakinus ' body . ( TV : " The Lost " )