Shadow Planet Killer
A Shadow Planet Killer is a fictional machine from the Babylon 5 television show and films, which was used to destroy planetary ecosystems.
At first sight, the Shadow Planet Killer appears to be a gigantic mobile cloud of dust and gas, capable of surrounding a planet (thus its other name, the Death Cloud). On closer inspection, this cloud is revealed as a cover which conceals a net-like matrix of tubes and beams. The Planet Killer expands this net around a planet, with the dust and gas cutting off any contact to the outside. The dust and gas are actually bio-nanobots.
Once this is done, various hubs around the net fire missiles at the surface of the planet. Instead of exploding on the surface, these missiles burrow down through the planet until they reach the core, where they explode. The results are increased vulcanism, massive seismic upheaval, and atmospheric contamination, which together kill off the ecosystem and render the planet uninhabitable and sterile.
Like other Shadow ships, the Planet Killer can phase in or out of hyperspace at any time, and may interfere with other ships' engines. It is also very difficult to detect.
The Shadows employed Planet Killers on several occasions during the Shadow War. The Interstellar Alliance forces were unable to damage or destroy any of the Killers at the time, and among the planets thus destroyed was the homeworld of Dureena Nafeel.
In the movie A Call to Arms, a Shadow Planet Killer left behind after the War was taken by the Drakh (an alien race, former Shadow associates) and brought to bear against Earth, but was destroyed by the lead ship of the new Victory Class destroyer which targeted and then rammed a crucial control center used to control the rest of the mechanism causing the device to be triggered early, thereby essentially firing upon itself and the Drakh within it. Prior to its use against Earth, the planet killer was tested by the Drakh against the world of Daltron 7.