Klaus IV is a planet, located next to Klaus III. It is the home planet of Mirage Koas, a party member from Star Ocean: Till the End of Time, as well as Marietta, Lieber, and Steeg, who are all members of Quark. While it was originally uninhabited, colonization efforts by the Klausians means that now one fourth of all Klausians live in bio-domes on the surface.
The fourth planet in Klaus System, Klaus IV has an atmospheric composition that is almost completely made up of carbon dioxide. Klaus IV has an axial tilt of 11.2', is 1.8 AUs from its parent star, and has a gravity of 0.6 G. Although it used to be sterile and devoid of any life forms, as the population of Klaus III increased, colonization proceeded, and now one fourth of all Klausians live in habitation domes constructed on this planet. The atmospheric composition and gravity of the areas underneath the habitation domes are adjusted to resemble that of Klaus III, and therefore life is possible underneath the domes without any noticeable difference. The total number of Klausians living in the galaxy at present is estimated at around twelve billion.