Arcta is an ice planet in the Cyrannus galaxy that appears to have been uninhabited prior to the arrival of Dr. Ravashol. A brilliant scientist, Dr. Ravashol bred clones to assist him in his work, known as Theta class lifeforms ("Thetans"). These Thetans have created large underground excavations for their small city, since the surface is inhospitable due to di-ethene storms at places like Deathpoint Plateau.
The Cylons later established a garrison on Arcta using Dr. Ravashol's invention of the Ravashol pulsar as an offensive weapon. Both the pulsar and the Cylon garrison are later destroyed in a joint effort featuring a strike team from Galactica and the Thetans. Despite the previous Cylon incursion into Arcta, Ravashol reaffirms his support of the Thetans and claims to have developed technologies to prevent the Cylons from reasserting their influence (TOS: "The Gun on Ice Planet Zero, Part II").