Virus/New Era
The Virus was the apocalyptic superweapon used to establish the base for the Traveller: The New Era role playing game.
Virus was the "final solution" superweapon developed under Lucan's direction and intended to end the Second Civil War (1116-1130 Imperial), also referred to as the Final War. End the war it did, but not in the way Lucan may have intended.
Originally developed at Research Station Omicron from sentient chips originally found on Cymbeline, the Virus was inadvertently released by Archduke Dulinor's hamhanded actions at the head of his Coronation Fleet during his final bid for Capital - the commandos that had stormed the facility, seeking to steal research data, never realised that they were not only transmitting data about the Virus superweapon - they were also transmitting the weapon itself.
For most areas of the former Third Imperium, exhausted as they were from the struggles of the Final War, the crash was hard and fast, especially near the areas the weapon was released.