A Virus Bomb is a potent Imperial biological weapon and weapon of mass destruction, commonly used to carry out Exterminatus actions during the Great Crusade and Horus Heresy periods of the late 30th and early 31st Millennia, most memorably during the Istvaan III Atrocity.
They were largely replaced in Imperial arsenals by the more potent Cyclonic Torpedoes by the time of the late 41st Millennium, but have still been deployed in recent memory, such as upon the Stalinvast Hive World in 273.M41 following a Genestealer infestation.
Virus Bombs deploy a hideous genetically-engineered pathogen called the Life-Eater virus intended to exterminate all forms of life in an inhabited planet's biosphere. The pathogen, once released in aerosol form from the Virus Bombs, is extraordinarily virulent, capable of infecting every living thing, including flora, fauna and even bacteria on an entire world in only solar minutes if 100% orbital dispersal is achieved. The pathogen can penetrate even sealed environment suits, including Power Armour.
The virus is designed to violently lyse living cells, essentially causing infected organisms to "melt" into a contaminated soup of organic matter. Entire forests and other plant matter can be reduced to this sludge in a short period of time, and individual animals die excruciating deaths as their bodies rapidly decay around them. The incredibly rapid breakdown of organic matter results in the steady release of great volumes of highly flammable natural gas, much of it composed of methane.
Eventually, as the contamination spreads across the surface of the world, a single spark, a single lightning strike, or an intentional incendiary event, will cause this gas to ignite, sweeping the planet with an apocalyptic, global firestorm. This intense heat will scour the world's surface back to bare rock as well as eradicate most of the remaining oxygen in the planet's atmosphere if it was habitable by Terran life.
In some cases, the lifeless Dead Worlds that are all that remain of planets that have suffered a virus bombing still prove valuable to the Adeptus Mechanicus after their violent death. These planets may be transformed into Mining Worlds or even prepared for a new round of terraforming to make them habitable for Imperial colonists once more.
Second War for Armageddon
During the Second War for Armageddon in 941.M41, Armageddon's Planetary Governor, the Overlord Herman von Strab, maintained a secret stash of ancient Virus Bombs that had originally been collected millennia before when his family had first led the colonisation of the Hive World. Once unleashed on the invading Greenskins they took a terrible toll, but their extreme age had degraded the stocks of Life-Eater pathogen within, and so the death rate among the Orks was nowhere near total.
Even worse, like many biological and chemical weapons, the shifting winds caused some of the pathogen to infect many members of the Astra Militarum regiments leading the Imperial defence, ultimately leading to as many deaths among the defenders of Armageddon as among their foes.
Inquisitor Mikhail Dinalt
On an undesignated frigid Feral World in the Segmentum Tempestus in 958.M41, Inquisitor Mikhail Dinalt of the Ordo Malleus ordered the planet to be viral bombed from orbit. Two Terran years earlier, a member of his Inquisitorial entourage had become stranded on the planet after "falling from the sky", and was being worshipped as a goddess by the primitive natives. Dinalt judged the local tribes to be engaged in heresy and carried out an Exterminatus action upon the world.
- Galaxy in Flames (Novel) by Ben Counter
- The Flight of the Eisenstein (Novel) by James Swallow, Ch. 9
- Inquisitor (Novel) by Ian Watson
- Ice Guard (Novel) by Steve Lyons
- Pandorax (Novel) by G Z Dunn