The Justaerin were the elite Terminator cadre of the Sons of Horus, the black-armoured killers who formed the Warmaster's most trusted and most feared warriors. Where their Legion brothers wore sea-green, the Justaerin went to war in funerary black, a colour of menace that marked them as the personal executioners of Horus's will.
Led by Ezekyle Abaddon, First Captain of the Legion, they were the tip of the spear in every great undertaking, thrown against objectives no other unit could break. Clad in Cataphractii plate and armed with the finest weapons the Legion could provide, a handful of Justaerin could shatter formations many times their number, and their presence on a battlefield signalled that Horus meant to see a thing done at any cost.
At the Drop Site Massacre and in the boarding actions that defined the war, the Justaerin earned a reputation for merciless efficiency. They embodied the pride and the doom of the Sons of Horus alike — superlative soldiers bound wholly to a master who had turned against everything they had once been raised to protect. In their black armour marched the future of the traitor Legions.