Haliard

 was a worker on the Cimmeria IV mining base. He and his fellow workers, Orllensa and Ferras, were responsible for setting up and activating a series of mini-suns in orbit around Cimmeria IV in preparation for planetary mining.

When the EPU array to power the suns was activated, an unknown force threw the system out of alignment. Orllensa had just enough time to send a distress call before the base was plunged into blackness. That same unknown force then burned out the eyes of everyone on the base. Haliard couldn't handle the pain and blindness, and went insane.

Soon after, the Eighth Doctor and Charley arrived in the company of ROSM -- a rescue ship. Sensing that there were aliens at work, ROSM assaulted them, but the same particles that blacked out the base disabled ROSM.

In the meantime Haliard was found by the aliens: Cimmerian healers trying to hide from their persecutors, the Solarians. The Cimmerians had not intended to harm anyone, but they had been hiding in the dark for so long they had forgotten what eyes were. The Cimmerians healed Haliard's eyes and mind, and asked him to stop The Doctor from realigning and activating the EPUs. ROSM's disabled state gave the Doctor enough time to finish the repairs, bringing light -- and the Solarians -- back to Cimmeria IV.

Haliard convinced the others of the Cimmerians' good intentions, and the other base workers were also soon healed. Luckily, the ancient persecution from the Solarians also proved to be a misunderstanding, and the base crew were able to pack up and head home. (BFA: Embrace the Darkness)