At the film's beginning, the ship, commanded by CaptainClark Terrell with executive officer CommanderPavel Chekov, is searching for planets suitable for use in the Genesis Project. This search brings the vessel to Ceti Alpha V, the planet on which Khan and his followers are exiled in the Star Trek episode "Space Seed". Khan captures Terrell and Chekov, both of whom he brainwashes with Ceti eels, before taking control of the ship. Khan maroons the ship's crew, save Terrell and Chekov, on Ceti Alpha V.
The disabled Reliant following the Mutara Nebula battle in Star Trek II
Under Khan's command, Reliant inflicts substantial damage on the USS Enterprise. The ships' engagement concludes in the Mutara Nebula, where the Enterprise severely damages the Reliant (see image at left). Khan eventually activates the Genesis Device in the hope that the resulting detonation will also destroy the Enterprise. The Reliant is destroyed, although Captain Spock's self-sacrifice allows the Enterprise to escape.