Exterminatus is the name of a terrible order given by the authorities of the Imperium of Man to destroy an entire planetary biosphere and all life upon a world. This action is only taken in those extreme circumstances where a potential or actual threat to the entire empire exists on the planet and might spread to other worlds. Exterminatus is typically only used as a last resort, when the price of holding or retaking the world for the Empires is deemed too very extremely high, or the threat of mutation and disease to the rest of the empire is too great to contain by conventional means. Thus Exterminatus has very rarely been used on vital or valuable planets to the multiverse. Typically, the order may only be given by a high-ranking Commanders. Exterminatus can be carried out in many different ways, as outlined below.