Caste

The Silurians operated on a racially-based caste system which included scholars and warriors. (COMIC: The Lost Dimension)

Ice Warriors had a feudal-like caste system which included Ice Lords (TV: The Seeds of Death) and an Empress. (TV: Empress of Mars)

Eutermesans were inducted into different castes. Such castes included management, food production and research workshops. (AUDIO: The Creed of the Kromon)

The Inter Minorians were divided into two castes: an upper class and the menial Functionary. (TV: Carnival of Monsters)