Krarg

Krargs, also known as Kraags, (PROSE: Shada) were creatures made of crystallised coal.

Biology
They were large, strong, semi-intelligent lumbering creatures with vivid red eyes. They were able to withstand high amounts of energy and could burn with a touch. When more Krargs were needed, they were created in large vats of heavy green gases that solidified coal over a skeleton. They had space carriers with smaller ships. (WC: Shada)

History
Delegates representing the Krargs attended the Armageddon Convention at Laputa in 1609. (PROSE: The Empire of Glass)

Krargs were used by Skagra as his own personal army. (WC: Shada) The Fourth Doctor saw a Krarg imprisoned cryogenically on Shada, noting it was strange how a lava creature could be frozen. (PROSE: Doctor Who and the Krikkitmen)