Missile Destroyers were aquatic repulsorcraft that were used by the Galactic Empire as the anti-air units in its aquatic navy.
They typically patrolled the seas around Imperial installations, accompanied by Imperial scout frigates serving as escort vessels, in order to protect against surprise attacks from Rebel starfighters or pirates.
Missile Destroyers under the command of Darth Vader were used during the Reytha campaign in 0 ABY.
Missile Destroyers appear in the 2001 video game Star Wars: Galactic Battlegrounds and its 2002 expansion pack Clone Campaigns. They may be built during the Galactic Empire campaign or in multiplayer.