There are several races in the Beyond The Impossible universe.

Immortal races

Gods: immortal beings with vast mind over-matter powers. First seen in BTI 002

Demigods: offspring of a God and a member of another species. Typically possessing special powers and/or immortality. First seen in BTI 116. Note that not all demigods are immortal.

Eden: gold-skinned humanoids created by the Sumerian gods by reverse engineering the genetic code of the Drylon. Currently extinct. First seen in BTI 323

Mortal races

Drylon: a powerful alien race that conquered the known universe but disappeared 5 billion years ago. Currently extinct. First mentioned in BTI 001

Humans: evolved on planet Earth. The last common ancestor of all sub-species lived between 600,000 to 1 million years ago.
Notable sub-species include:
-Earth humans:descendants of the origiginal pupulation. Unlike other sub-species, they still have an appendix. First seen in BTI 002
-Olympian humans: the dominant species of the Olympian Galaxy. Visually indistinguishable from most variants.
-Myridians: humans native to planet Myridia, genetically modified to be stronger than regular humans. First seen in BTI 022
-Aquilians: descendants of Zeus living on planet Aquilia. They have white hair and electrical powers.
-Egyptians: living in the galaxies under control of the Egyptian pantheon. They have second gallbladder, unusually high bone density and a vestigial nictitating membrane First seen in BTI 116
-Thalassians: able to breathe underwater, one of the species living in the Aegean Galaxy. First seen in BTI 393

Demons: red-skinned humanoids from planet Hell, created by Marduk one billion years ago. First seen in BTI 024

Ichthyians: one of the most common races of the Aegian Galaxy, they breathe only underwater and have the tail of a fish from the waist down. Named in BTI 506, first seen in BTI 507

Laestrygon: exterminated by Kronos for worshiping the Drylon as gods. Mentioned in BTI 213

Lamians: humanoids with snake bodies from the waist down, seen in the Aegian Galaxy (BTI 154) and the Abydos Galaxy (BTI 196)

Lampyrian: all-female humanoids descending from the union between Harpies and Zeus. Blue-skinned, with bat wings and extremely short lifespan. First mentioned in BTI 026

Lar: grey-skinned humanoids of unknown origin, active in the Olympian Galaxy for at least the last billion years. Boreas is the only known planet with a large population of Lar. First seen in BTI 118

Aurochian: minotaur species mostly living in the Athenian Federation. First seen in BTI 260

Naga: half-humanoid half-snake race living in the Naqada Galaxy. First seen in BTI 326

The Many: all-female species artificially created by Talas Khanos by reverse-engineering the Lampyrian genetic code, used as a living biological weapon. Currently extinct. First seen in BTI 003

Animal species

Dragons: giant feral animals bred by Artemis for sport. First seen in BTI 066

Harpies: non-sapient species native to the Olympian Galaxy. Blue-skinned half-bird half-humanoid, they can survive in space and have a very short lifespan. Nearly extinct in the wild; progenitor species of the Lampyrians. First seen in BTI 045