The Dark Crystal (1982)
The Skeksis are spawns of the species UrSkeks who took control of Thra after a tumultuous conflict with theMystics who also spawned from UrSkeks during the burning light emitted from the Crystal during the lastGreat Conjunction.
When prophecies revealed that the Skeksis tyranny would end when the missing shard of the Dark Crystal is one day found and restored by the Gelfling people, the evil Skeksis race took the Gelfling tribe by force. With the help of their tribe of Garthim warriors they manage to kill all but two survivors, Jen and Kira. The Skeksis placed several copies of the missing shard all over the mountain of Thra, in hopes that the Gelfling would never be able to restore the natural order of their world and the Skesksis rule would last for all eternity. The wicked Skeksis live off of the essence of others, which they obtain from the captured Gelflings and Podlings. (wikia)