An individual H'rulka is actually a collective organism, much like a Portuguese man-o-war. It is a gargantuan collection of smaller organisms with their own specialized functions, such as tentacles, sensory organs, food filters, and brains. Among these specialized parts are biological radios, allowing them to send and receive radio transmissions. The entire mass resembles an ivory-colored jellyfish between 200 and 300 meters (660 to 1,000 ft) across and weighing hundreds of thousands of tons, suspended in the air by gas bags. Its body also hosts numerous parasites and symbiotes, themselves on the same scale as humans.
Their nature as collective beings allows them to split into multiple smaller, but still functional, versions of themselves. When threatened, H'rulka can split into twelve sub-colonies. Called "divergence," this process is irreversible and causes extensive loss of identity, knowledge, and memory, so H'rulka consider it highly traumatic and only do it when absolutely necessary.
H'rulka breathe hydrogen, and they find water and free oxygen poisonous. They have some metabolic use for carbon, and can extract it from various compounds they consume.
H'rulka are filter-feeders, taking in and eating organic compounds and plankton from the atmosphere. They also feed off methane and ammonia taken in from the air.
As collective beings, H'rulka lack a hard-and-fast concept of the individual. They have permanent names, but give numerical designations, subject to change, to virtually all other things. In addition, they do not occupy permanent jobs and have no leadership roles to speak of, instead deferring to the most qualified H'rulka when the need arises.
Their environment on gas giants also contributes strongly to their psychology. Closed spaces do not exist naturally on their homeworld, and as a result all H'rulka have a strong sense of claustrophobia. They also think of most other sentient creatures as "vermin." This has more to do with the enormous size discrepancy between the H'rulka and nearly every other sentient species than actual contempt or bigotry, though they do find most terrestrial creatures to be strange and disgusting.
The H'rulka are native to a gas giant very similar to the planet Saturn. Its atmosphere consists mostly of hydrogen and helium, with traces of ammonia, methane, water, and other chemicals. It also contains very small amounts of metal, which they extract from the air to build their technology. The H'rulka reside in the atmosphere's upper reaches, where the temperature is around 12 degrees Celsius. The "surface" gravity of their home planet is about 0.9 g.
The H'rulka originated as herd animals confined to their homeworld. While sentient, they were unable to develop technology due to the lack of metal or oxygen on the planet. This changed with the arrival of an alien race called the Starborn at some point between 10,000 and 13,000 BCE. The Starborn provided the H'rulka with the means to extract metal from the atmosphere and to develop spaceflight before leaving for parts unknown. Not long after this, the H'rulka encountered and were subjugated by the Sh'daar.
H'rulka technology is different from, and considerably more advanced than, many other Sh'daar client races, possibly due to its different origin. Their technology is also constructed on a massive scale due to the H'rulka's great size. They use nanotechnology as a building material, as well as networks of metal and hydrocarbons.
H'rulka technology uses quantum power taps, which draw energy from the quantum foam by rotating two microsingularities around each other very rapidly.
H'rulka spacecraft are made of nanomaterials capable of rapidly changing shape. A typical H'rulka warship is an ovoid craft twenty kilometers long, carrying twelve crew members in a two-kilometer "cockpit." These warships can split into twelve pieces just as their designers can, each crewed by a single H'rulka; unlike the H'rulka, these pieces can reunite.
These spacecraft are shielded and propelled by the manipulation of spacetime and singularities, as are Turusch ships. However, their Alcubierre drives are highly advanced, and can advance much deeper into a solar system than most other such drives can.
H'rulka ship weaponry consists mainly of singularity projectors, which fire knots of spacetime compressed into black holes at opposing ships, essentially tearing them apart. They also use particle beams as point-defense weapons.