In the first series, The Black Adder, set shortly after The War of the Roses, the central character is Prince Edmund, known as "the Black Adder", son of the fictional King Richard IV of England.
In Blackadder II the central character is Edmund, Lord Blackadder, a nobleman in the court of Elizabeth I of England.
In Blackadder the Third the central character is Edmund Blackadder, Esquire, butler to the Prince Regent.
In Blackadder Goes Forth the central character is Captain Edmund Blackadder, an officer in the British army during World War I.
Various one-off specials have introduced other Blackadders throughout history, from the Roman legionary Blackadicus to a Blackadder in the distant future who becomes ruler of the universe.