There is still no consensus on what exactly each of the riders represents, but they are often referred to as the Plague (riding a white horse - also known as the Conqueror), War (on a red horse - also known as Discord), Famine (on a black horse) and Death (on a pale horse). God calls them and empowers them to sow chaos and destruction in the world. Horsemen appear strictly one after another, each with the opening of the next seal - the first four of the seven seals of the book of Revelation.