The Cimmerians had a strong level of telekinesis at a molecular level. This included the ability to pass their bodies or the bodies of others through solid materials, including concrete and rock.
Their telekinesis also allowed them to heal wounds. Given enough strength and energy they could heal any injury and even rebalance the minds of the insane. Their race had a compulsion to use their healing power on anyone suffering from hurt or disease, to the point that the Cimmerians would exhaust themselves before stopping. In extreme cases they would continue healing until they died. (AUDIO: Embrace the Darkness)
The Cimmerians had the means to project particles of an unknown type that would "take the light." These particles would disrupt electronics and could drain power reserves. Heavy concentrations of these particles would also burn out the eyes of people exposed to them. The ROSM AI/ship had a means to counter the particles' spread and effect.
Their data storage was an organic liquid matrix that would invoke the desired memories/thoughts when ingested. Reading their records required a person to eat a soup-like substance and "taste" the memories. (AUDIO: Embrace the Darkness)
In ancient times the Cimmerians were merely a talented sub-group of the Solarian race. They freely offered their healing services for the good of the people. The race was hit by a plague that could not be cured by healing. As the plague spread, more and more victims came to the healers for help, and the healers soon found themselves overwhelmed and stretched beyond their ability to recover. They recognised that they must flee or their compulsion to heal would drive them to their deaths. However, the plague victims followed them. Eventually the fleeing healers landed on Cimmeria IV and projected a cloud of particles large enough to blot out the Cimmerian sun. The Solarians' sail craft couldn't follow without the sunlight, and the healers were lost to them.
Over many generations the healers hid in the darkness, afraid of being found by the Solarians. They evolved enough that they forgot the concept of sight, and switched to taste as their central sense.
A Throxillian company believed Cimmeria IV was a prime target for mining, with substantial mineral wealth and no native life. They established a base on the planet and built a set of mini-suns in orbit around the planet, powered by a set of Energy Projection Units on the surface. Fearing the light of the suns would lead to their immediate re-discovery by the Solarians, the Cimmerians sabotaged the EPUs and blacked out the base. A distress signal from the base brought the ROSM rescue ship, bearing the Eighth Doctor and Charley. ROSM's assault units subdued the Cimmerians long enough for the Doctor to realign and activate the mini-sun system.
The Solarians, finding the planet to be newly lit, swiftly returned and took umbrage at the human presence. They were astonished to find that their brethren were still alive, and quickly dropped hostilities.