It's called Power of the Dark Crystal.
Set hundreds of years after the events of the first movie, when the world has once again fallen into darkness, "Power of the Dark Crystal" follows the adventures of a mysterious girl made of fire who, together with a Gelfling outcast, steals a shard of the legendary crystal in an attempt to reignite the dying sun that exists at the center of the planet.
It couldn't possibly be better than the original: