Planet Prime was created by the High Being named Life, who then created three moons. Life designed the planet to be full of plantlife, and it was the home for many Rahi and Matoran. After Life created many other universes and populated them with species, Life resided on the top of the Mountain.
After a hundred thousand years, Death gained control of the planet and put Life into a coma. As a result, the planet, which was tied to Life's life force, mostly ended up beneath an ocean of lava, originating below the crust.
Originally, the planet was full of plant and animal life. However, Death transformed it into a planet almost devoid of life, covered in an ocean of lava from below the planet's crust. There is currently no animal or plant life except in the Gatnui swamp beneath the Mountain.
Death's power generated a lightning storm above the Mountain, stemming from the Palace of Death.
The planet is so large that it would have long ago collapsed into a star had its interior not been entirely hollow. The planet is comprised of a crust layer, then a layer of molten magma, which generates the planet's heat, then a hollow interior. It is possible that there is a small core as well, which may be home to some life-forms.
- Planet Prime, its three moons, and Xenia's orbiting asteroids are the only locations in the entire Prime Universe.