The Dark Crystal is a science fiction film not set within the Solar System which was released in 1982 and is directed by Jim Henson.
A thousand years ago, the planet Thra used to green and the vegetation plentiful but that was before the Crystal was damaged. During the last convergence of the three suns, the urSkeks damaged the Crystal. A small shard of the Crystal broke off and became lost. The land around the Crystal turned to wasteland and the urSkeks split into two races, the Mystics and the Skeksis. The Skekis, tall creatures with faces like birds kept control of the tower that house the Crystal. The Mystics, a crouching sloth like creatures retreated from the tower.
The convergences of the Suns are due soon and if the Crystal is not repaired, the Skeksis will rule the planet forever. According to legend, a Gelfling will repair the Crystal and thus break the Skeksis control over the planet. The Gefling is Jen who begins the mission by first obtaining the missing shard then journeying to the Tower to join the pieces. Along the way, he is assisted by a female Gefling called Kira.
All the characters are puppets, there are no humans or computer trickery in the film. The team behind the film are more famous for the Muppets and Farscape. In World of Warcraft, Blizzard has paid homage to the film by creating the Arakkoa who dwell mainly in the Terrokar Forest, Outlands.
A series of the Dark Crystal is currently in production by Henson Studios, who were the original pupeteers for the original film. The series is expected to be 10 parts in length and is exclusive to Netflix. All you need to know can be seen in this Youtube Video.
When the Dark Crystal was splintered, the UrSkek was split into races, the Skeksis and the Mystics. Only by putting the shard into the crystal at the moment will the Skeksis and Mystics merge. If one of the Skeksis or Mystics dies, their opposite number dies too. When the Crystal is whole again, the Mystics and Skeksis merge and become whole again. The Skeksis live all their lives in the Dark Castle so to speak. They have an army of beetles that they send out to do their bidding. They look like vultures and they eat any small bugs or creatures that they can find.
The Skeksis are immortalised at Arakkoas in Warcraft. The Arakkoas appear in the World of Warcraft - Burning Crusade and World of Warcraft - Warlords of Draenor expansions. The Arrakoas live on the planet Draenor but have not made the leap to Azeroth yet. Whilst the Arakkoas are enemies in Burning Crusade, players can gain reputation with the Arakkoas in the Warlords of Draenor.
The Gelflings are Elf inspired races that live on the planet of Thra. Jen believed he was the only Gelfling left on the planet but fortunately, he came across Kira, a female gelfling. Together, the two Gelflings would see through to the end of the objective with Jen merging the broken shard with the main dark crystal.
The Mystics are slow creatures that make their way to the Dark Crystal. When a Skesis dies, a Mystic dies and vice versa. When Jen succeed in making the crystal whole again, the Mystics and the Skesis merge back into the UrSkeks.