Exterminatus is an attack from space intended to render a planet uninhabitable. It is the ultimate force used by the Imperium of Man to eliminate threats or to contain major heretical events. Normally ordered by an Inquisitor, Exterminatus is only chosen when the chance of being able to hold a planet has been reduced to almost zero. It is not considered a combat weapon, and although it has been used as such, these uses are limited.
Exterminatus takes place in a variety of ways, and no method seems to be more common than another. In a typical example, the Exterminatus begins with an orbital bombardment of a world, taking out anti-ship weapon platforms as well as any shielding. Following this, a salvo of virus torpedos is launched, dispersing in the atmosphere and spreading all over the planet. In some cases, the virus bombs will be replaced by a mixture of extremely flammable gases designed to burn a way a planet's atmosphere. Either can be supplemented with direct fire against the planet. By the time the procedure has finished, all that remains of the planet is a blasted rock, stripped of its atmosphere, and devoid of all signs of life.