Castigation of Terentius
The Castigation of Terentius was a campaign of the Great Crusade.
The campaign was waged against Vatale Gerron Terentius, a warlord of the Halo Stars who had sworn fealty to the Emperor but had since gone rogue and betrayed his vows. Terentius began to attack world already brought into the infant Imperium and created his own rebel empire. Thus the Imperium responded with its full wrath, with the Emperor personally ordering that Luna Wolves Primarch Horus Lupercal deal with the traitor.
When Horus struck at Terentius' empire, he attacked with not only his own Legion but also with elements of the Night Lords, Iron Hands, and Alpha Legion. The first blows fell far inside the borders of Terentius empire when ships inside the Hecuba and Hilicia Systems suffered reactor failures. The ensuing naval disaster consumed two battle fleets and stranded hundreds of thousands of reinforcements. On Yeno Prime Terentius' chief lieutenants disappeared along with their command staffs. On Jubal, the spire Forges collapsed as tectonic charges detonated in their foundations. On hundreds of planets disasters and cataclysms crippled Terentius' empire. These acts bore the mark of the Alpha Legion.
Terentius however was a skilled commander and was able to reform and redistribute his forces. As he did this, ships from the edges of his empire reached the core of his realm but were filled with tens of thousands of corpses. The surviving crews brought word of entire worlds decimated by midnight-clad warriors. Terror spread throughout Terentius' empire despite his best efforts to contain the news. To compound this disaster, Iron Hands began to move on his bastion worlds. As he moved to counter-attack, his strikeforce was intercepted and destroyed by the Luna Wolves. It is said that at this moment, when he realized that he could not win, that Horus came for him personally.
A Sons of Horus fleet arrived from the Warp and within minutes annihilated Terentius' command fleet. Horus himself teleported aboard Terentius' flagship, accompanied by 50 Justaerin and slaughtered all they found. Terentius died unrepentant, laughing as he was impaled by the Talon of Horus. With their leader dead, Terentius' rebellion crumbled. However Horus, his pride slighted, acted uncharacteristically harsh and ordered the Night Lords, Iron Hands, and Ordo Reductor to decimate every one of the remaining rebel worlds. The fate of Terentius' rebel empire would serve as an example to all who sought to defy the Emperor.