Planets and alien species (Earth-4)

Three-Arm Tyrants: a scientifically advanced species originally from deep space that conquered Mars. Males are humanoid and have three arms, green skin, a single horn, and fangs, while females appear identical to pink-skinned human women. [Fantastic Comics #1]

Slave-Giants: Giant humanoids around 150 feet tall with religious tendencies. Three-Arm Tyrants use Slave-Giants as servants. Slave-Giants are very susceptible to the allure of a beautiful young woman, especially the Three-Arm females, and they worship an idol in the form of a Three-Arm female. [Fantastic Comics #1]

Dwarfs: Tiny humanoids around six inches tall who consider themselves the true people of Mars. [Fantastic Comics #2]

Carnicantileia: a large man-eating monster similar to a cross between an alligator and a snake that lives in the swamps. [Fantastic Comics #3]

Serviles: a birdlike species without beaks that communicate telepathically through thought-wave helmets. [Fantastic Comics #5]

Heidites: huge, dragonlike monsters from Mercury's hot side that are the enemy of the Serviles. [Fantastic Comics #5]

Servil: the city of Mercury's birdlike species. [Fantastic Comics #5]

Caspia: a prison planet run by the Vargs, a birdlike humanoid species, where the worst criminals of Earth are sent. The original prison on the planet is known as the Rock, because it is a prison built within a tall pinnacle of rock in the midst of the Boiling Sea. After the Vargs are shown to be using the prisoners as human sacrifices, an agent of Frontier Security responsible for Caspia destroys the Rock with a burst from a ray cannon after escaping from it. [Charlton Bullseye v2 #8]