The World of the Dark Crystal is the Homeworld of the Lords of Change.
Just look at the physical appearances of the Skeksis and compare them with Tzeentch's Lords of Change from Warhammer
. They also both have a fondness of court intrigue and plotting. It also wouldn't be too hard to see that the planet is one within the Eye of Terror.
- So, are Garthim Chaos Marines then?
- Since we are dealing with Tzeentch's minions, the Garthim are probably the equivalent of the Thousand Sons' Rubric Marines: empty armor containing a trapped soul. They are described as "living suits that are still capable of fighting and receiving orders from their masters and with no fear and no will of their own they make perfect bodyguards and guardians." Sounds like a Garthim.
The Skeksis discovered wormhole travel at some point in the past.
This was obviously when they were far more numerous, and was no doubt one of SkekTek's masterpieces: unfortunately, the Skeksis pioneers that entered the wormhole never reported back, so the Emperor had the project discontinued. However, unbeknowst to him, they actually had arrived on a planet in the Farscape
universe. Pausing only to officially rename themselves the Halosians
, they then raided the local spaceport, took the best-armed of all the ships docked there, and flew off into the Uncharted Territories to carry on with their lifestyle of conquest and backstabbery.
- I have a similar theory below.
The Halosians in Farscape
came from the same world as the 
Somehow, Halosians evolved from Skeksis who left their urSkek forms somehow. Wishing to explore other worlds just as the urSkeks had explored Thra, the Halosians created space travel, and the planets surrounding Thra and the world of the urSkeks are shown in Farscape.
- Both of these theories exist because the skeletal structures of the Skeksis puppets were used to make the Halosians,
The Skeksis did some extensive remodeling to the castle to cover up the old style
This is what falls apart off the castle at the end
The final shot of the castle surrounded by lush landscape is years after the climax
For those of us who don't buy the vegetation suddenly appearing outside.
They left the planet via beams of light at the end...
The world of the Dark Crystal is in the Alpha Centauri star system.
Due to the fact that the three suns bare a vaguely passing resemblance.
The Podlings are the descendants or ancestors of Fraggles
They live underground, they're tiny, good-humored, fond of food and song, and created by Jim Henson! Bam!
The Gelfling are a result of breeding between elves and halflings.
Just look at the name of their race.
There are still some Skeksis and Mystics on Thra after the film's end.
One of the episodes of Jim Henson's Creature Shop Challenge
has contestants building Skeksis that were exiled from the castle centuries ago. If there really were outcasts who pre-dated the Chamberlain, and any of them survived until the Great Conjunction, they may not have had the chance to return to the castle in time to be there for the Crystal's healing. Their Mystic counterparts, in turn, may have left the Valley to become solitary hermits at the same time the corresponding Skeksis was exiled: something the Chamberlain's counterpart would also have done, had their community not known the Conjunction was imminent.