Shadow Kin

The Shadow Kin were a race of fire-type humanoids that could only survive physically with the presence of a shadow. They were led by the Shadow King, Corakinus.

Biology
to be added

History
The Shadow Kin emerged on the planet Rhodia amidst a war between the Rhodians and 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 force were forced back through the tear from where they came which the Doctor subsequently sealed. Corakinus warned, however, that the Shadow Kin would return. (TV: For Tonight We Might Die)