Sky demon

The sky demon was a mythological figure by which the Captain, apparent ruler of Zanak, frequently swore.

His oaths concerning the sky demon included:
 * By the sky demon
 * By the beard of the sky demon
 * By the blood of the sky demon
 * By the left frontal lobe of the sky demon
 * By the raging fury of the sky demon
 * By the curled fangs of the sky demon

Taken together, these oaths suggest a fearsome creature. (DW: The Pirate Planet)

Behind the scenes
Deleted material from The Pirate Planet would have established that the Captain's culture believed that the sky demon, a mythological devil, captured their souls after death. (INFO: The Pirate Planet)