The Hydran Kingdom is inhabited by a single race, the Hydrans. They are one of the more 'alien' dominant races in the known galaxy. The atmosphere of the Hydran homeworld is rich in methane, which they breathe. This would be uncomfortable (or fatal) to most Federation species.

Hydrans have three arms, three legs and three eyes. Their skin is tough and leathery. Hydrans have three sexes, which are generally referred to as Male, Female, and Matriarchal. All births result in triplets (one of each sex) that are cared for by the Matriarchal. Males tend to dominate the command and technical positions, while females form most of the labor force, fighter pilots, and ground combat troops. Some females can hold command positions, or even the throne. Matriarchals are non-sentient and never hold positions in business or industry.

The Hydrans have a Pantheon of minor gods, some of which are of a higher order (and the order may change as different political factions come to power within any given group.) Each household has its own god or gods, as does each starship, squadron, and fleet.

The Hydran government is a Monarchy. The lines of succession are quite complex since the Hydrans are anything but monogamous. The Royal Family consists of approximately 30,000 beings, with some 1,200 Princes (both male and female.) Theoretically, any one of the princes could ascend to the throne. There is an extensive nobility that involves itself in internal politics and a strong Civil Service that actually runs the day to day affairs of government.

The Hydrans were once conquered by the Klingons and Lyrans and held as a client state for nearly 50 years. Powerful merchant guilds setup the "Lost Colonies" during this time and eventually developed the technology and resources to remove the Klingons and Lyrans from their space.

Despite their odd appearance, Hydrans are almost human in terms of their philosophy and disposition. In general, they don't attack unless provoked, and are more interested in scientific exploration than territorial expansion.