Shadows

Krogor was a shadow-based hive mind species who lived on the planet Noumeia in early days of the universe. They were usually incorporeal, but were able to form themselves into certain shapes in order to interact with humanoids.

They fought a long war against the Light, with the two species unable to communicate due to their differences. They were encountered by the First Doctor, Barbara Wright, Ian Chesterton and Vicki Pallister in the last days of their species, with the Doctor trying to help the two species to communicate. (AUDIO: The Dark Planet)