Starchaser: Legend of Orin

Set (largely) on the subterranean Mine-World, a band of human worker are treated like slaves under the power of the evil overlord Zygon until one, Orin, unearths the hilt of a mythical sword that only he can master. Escaping the planet, he runs into the rogue smuggler Dagg and a pair of helpful droids and the princess, who all team up to return to the Mine-World with a plan to defeat Zygon and free Orin's enslaved people.

(Have we heard this plot before?)

Starchaser: Legend of Orin is an animated homage to Star Wars: A New Hope that doesn't even bother to use any mention of Empire, Rebellion, or a lot of otherwise "core material" that Starchaser could have. Also of note is of all the things that Lucasfilm sued people over wildly, this film seems to have (deliberately) escaped their notice then, and by now it's a little too late.