Blimp

The blimps are an ancient and long-lived alien race that took up residence on Jupiter in the distant past. They protect their new home by directing comets into other planets, which eventually led them into conflict with Earth.

History
The blimps evolved on a Jovian planet they called Firsthome. For at least a billion years, they protected their planet from "snowstrikes" (cometary impacts) by directing incoming comets into their sun, which eventually aroused the ire of the star's native plasmoids. The plasmoids, refusing to destroy the blimps outright, responded with a series of targeted solar eruptions, driving the blimps from their homeworld. The evicted blimps tamed giant spaceborne aliens called magnetotorii and attached their moons to them, embarking on an an interstellar journey.

The blimps arrived on Jupiter around 330 million years ago, during Earth's Carboniferous period. They quickly settled the planet, which already had a thriving ecosystem similar to their own. They installed their moons in the planet's orbit as Jupiters innermost four moons, and used the Galilean moons to deflect comets. The blimps learned from their earlier mistake, and instead bombarded other planets in the solar system. One such comet struck the Earth at the end of the Cretaceous period, wiping out the dinosaurs. The blimps would later direct another comet at Earth in the early 23rd century, unaware that the planet was inhabited.

Technology
Blimps primarily use biotechnology. Their cities, for instance, are enormous organisms the size of small nations, which blimps inhabit by the millions. The cities are colonies of trillions of gas-filled creatures that form agglomerations not unlike coral. The blimps are able to biochemically guide their precise growth.

Uniquely, blimp biotechnology incorporates metal and robotics, as they are innately able to excrete waste metals into a complicated machine called a symbiaut. Symbiauts are essentially robots, controlled and programmed by the blimp that created them, made for specific functions. They generally have wheels, and were thus called "wheelers" by humans, but many are also able to move using blimp gravity technology.

Blimps have highly advanced gravitic technology that generates an antigravity force to manipulate objects. This force has a short range, forcing the blimps to maneuver Jupiter's moons in order to affect objects that are further away.