I have compiled a quick guide to the five species of The Fifth Civilization universe. CAUTION! The list below may contain some spoilers.
The trilogy begins in the year 2500.
KOTARANS — Marsupial-descended race. Have flat feet, long tails, a snout, and big ears. Often called “kangas” by humans because they resemble the kangaroos of Earth. They come from the planet Kotara, and are very militaristic. Their primary religion honors the three gods of Kotara: Bar’Hail the sky god, Fox’Lo the ground god, and Gri’Nelda the water goddess. Members include Commander Grinek, Observer Zil, and General Arlay.
NYDENS — Descended from avians. Nydens are distinguished by their feathery bodies, talon-like arms and feet, and a transparent bulb on their head that shines with the color of their emotions. Hailing from the planet Nydaya, the Nydens are noted for their pursuit of inner peace and their pacifism, traits that some of the other species despise. Humans sometimes disparage them as “pigeons” or “ducks.” Members include David and Stephen.
BAUXENS — Bauxens are descended from amphibians. They have rotund bodies that come in shades of green and are topped with a flat head and bulbous eyes. Inhabiting the planet Bauxa, the main focus of this race is trade, and they generally want to be on good terms with all of the known races. Sometimes disparaged as “toads.” Prince Duvurn Dedro is a Bauxen.
HUMANS — Primate-descended race. Live on the planet Earth. The last species to be contacted by the three technologically-advanced races, sometime around the year 2300. Kotarans usually call them "Earthmen." Notable humans include Nick Roan and Minister Kazumi Koda.
THE FIFTH CIVILIZATION — Canine-like aliens. Live on the fifth inhabited planet discovered, called Aaron’s Planet by the humans and Somoresh by the Kotarans. The Fifth Civilization consists mostly of pre-industrial tribes living in forests as hunter-gatherers. They have not yet adopted a universal name, but tribes include the Hedda and the Gohorma. Humans and Kotarans often call them by the epithet "jackals." Two Mountains is a member of the Hedda tribe.