Octa Butler [b. 219 BG) was the younger sister of Serena Butler the High Priestess of the Butlerian Jihad. Octa had a twin brother named Fredo who died in his teens. Fredo's disease was genetically based and she took care with her health and lived each day dreading that her life would come to a slow, painful end.
Octa was unlike her elder sister, being more sensitive, shy and docile. After Fredo's death she gave up her artwork, becoming a quieter, more pensive soul. She always had a crush on her flirt, Tercero Xavier Harkonnen.
When Serena was captured by the machines and presumed dead, Xavier started to see Octa differently and the two were married. Unlike her sister, Octa possessed a more submissive personality and lived on Salusa Secundus while her husband traveled on military campaigns.
After the heroic death of Xavier, due to the scandalous propaganda about his 'traitorous' death, Octa abandoned the disgraced Harkonnen name and reverted to her maiden name of Butler; she retreated to the City of Introspection.