Kieth, Lance, Hunk, Pidge and Princess Allura have successfully awakened the legendary robot guardian, Voltron. After countless battles, they've pushed back the forces of evil King Zarkon, freeing the Princess's home, planet Arus, as well as their sister planet, Pollux. But they couldn't save the princess of Pollux, Romelle, from the clutches of Prince Lotor. The Voltron force is dedicated to defense, and are unable to launch a full-scale assault on Planet Doom to rescue Romelle from Lotor's Pit of Skulls. Then, a batch of slaves arrives on planet Doom, and with them Romelle's last hope.