The Karthulian System is the training grounds of the original Paladins of Voltron filled with planets that have extreme natural environments to test each Paladin's skills as a pilot. It also appears to be the location of the Fripping Bulgogian, a restaurant favored as a hangout by the original Paladins of ten thousand years ago that has a table reserved for them, inscribed with their names and that of King Alfor. The Karthulian System is located in the quadrant overseen by the Mu, a family organization whose leader is currently Kythylian Mu.
- Yendailian: A planet constantly exploding with volcanic blasts. Used by the Red Paladin.
- Bluve: A planet covered in ice blizzards and blue crystals. Used by the Blue Paladin.
- Niloofar: A planet covered in sandy wind storms. Used by the Yellow Paladin.
- Griezian Sur: A planet covered in gigantic rain forests and home to the Muldoks, a species comparable in size to the Green Lion. Used by the Green Paladin.
- Talwar Six: A planet filled with enormous, labyrinthine caves create by giant space wombeasts before the species began its mating cycle migration four million years ago. Used by the Black Paladin.