The Mother Ship is a recurring element in the Raiden series. In the Raiden for PC English manual it is called the Vengeance. It is unknown if it retains that name throughout Raiden II, DX, III, and IV. In Raiden V, it is an all new carrier called the Bellwether, as seen on the radar battle map during the opening cutscene.
The Mother Ship is a huge flying fortress and aircraft carrier which serves as the base of operations for the World Alliance Military. It has a series of buildings on it's rear side and a large landing track on the frontal portion. It always appear at the beginning of every Raiden title, as the Raiden series of fighters take flight from it. It also appears halfway through the games, as the fighters land on it in order to fly to space.