12th Black Crusade - Gothic War

The Twelfth Black Crusade, or Gothic War, was a vast campaign launched by Abaddon the Despoiler which engulfed the Gothic Sector. It consisted of hundreds of planetary invasions and naval battles and only ended when Abaddon was forced to retreat to the immaterium with the arrival of Imperial reinforcements. It saw the destruction of several planets and four of the six Blackstone Fortresses as well as the deaths of billions of Imperial citizens.