 According to the Doctor Who Files book on the Cult Of Skaro, Dalek Sec was the Commander of the Seventh Incursion Squad and led the attack on the Mechonoids on Magella before being promoted by the Dalek Emperor.Dalek Caan was originally second in command to Dalek Sec, whom he overthrew after Sec became a Human/Dalek hybrid.He has the lowest pitched voice in the Cult, and is the most prominent Dalek of the revived series (having appeared in a total of six episodes).