Voltron: Defender of the Universe Season 1 Episode 61 Final Victory

Lotor activates his command center, Dark Doom Castle. Even with all his might, Voltron cannot fight off the entire castle alone. The team tries to hold on just long enough for Sven and Romelle to free the slaves. At the last moment, Coran flies to the rescue with the Castle of Lions in starship mode. While the fight rages, Sven sneaks into the evil castle alone to challenge Lotor personally!