The term "oprichnik" refers to members of a secret police force established by Tsar Ivan IV, also known as Ivan the Terrible, in the 16th century. This group was created to eliminate opposition and enforce the Tsar's authority, particularly among the nobility. Oprichniki were known for their distinctive black attire and their brutal methods, which included intimidation and violence. The oprichniks operated under the banner of the Oprichnina, a policy that allowed the Tsar to rule without the influence of the traditional nobility. Their actions contributed to a period of terror and repression in Russia, leaving a lasting impact on the country's history and governance.