Buckle up your buttholes buckaroos, because it's time for one of those rare moments where GW churns out something so bumcrunchingly awesome that even grizzled neckbeards can only shed manly tears for it.
The story begins Circa 811.M37, before any of the players that we know of were even born. Abaddon the Despoiler, fresh off his mini victory of the 6th Black Crusade (the one no one gave a shit about) was feeling pretty ok about himself and decided to attack the planet Mackan with the bulk of his forces to steal an Eldar artifact he needed to progress his plan--or at least look like he had a plan. So he rounded up his mates, Iskandar Khayon, Lheorvine Ukris and Telemachon Lyras and proceeded to open up a sectors worth of whoop-ass. The Blood Angels responded at Chapter strength with a few companies from a White Scars successor chapter, the Rampagers for back-up and that's it, since the High Lords couldn't get their shit together fast enough it was up to the Astartes to turn away the massive tide of chaos. It didn't go great.
The Rampagers didn't last long and even though the Blood Angels gave as good as they got - better, even - plus making a terrific account of themselves according to the death ratio, they just couldn't keep up with the numbers of the Black Legion by themselves unaided. After their last Captain on planet was unceremoniously relieved of his internal organs by the Warmaster of Chaos--Reclusiarch Jorus realized he had had enough of that "losing" shit and decided it was time for some payback.
The Awesomeness that followed
Thalastian Jorus immediately whipped his boys into shape, undeterred that the only fighting force of the Blood Angels left on Mackan was a bunch of howling and raving lunatics from the Death Company and the surviving Angels who had fallen to the curses of their chapter. Jorus was outmanned by a matter of thousands to one, he was easily outgunned by the sorceries Khayon could bring to bear and Lyras was a famous champion in chaos circles. The fact that the Chaos forces thought they were dead was little comfort and each of the boys under his command was a barely controllable bloodthirsty berzerker. Even for Blood Angels, things looked grim indeed...
For days, the blood-crazed Blood Angels waged a guerilla war with the chaotics, striking hard and fast before vanishing again, Raven Guard-style. After weeks of harrying the Black Legion, they had drawn enough of the Chaos forces for Reclusiarch Jorus to make his final daring thrust into the heart of Chaos. Like a murderous tide, the Death Company fell upon the Honour Guard of the Warmaster and tore them to ribbons pushing back Khayon and Lyras until it was just Thalastian Jorus and Ezekyle Abaddon face to face, with Ukris dying in the fighting.
And in a furious blaze of glory the little Reclusiarch that could achieved what so few can match--gravely wounded the warmaster enough that he had to quit the field. In fact, the wounds inflicted were so terrible that Abby still bears the remnants of the strike on his body as a strange mark of pride - or as a means of remembering a particularly valiant enemy. As the Reclusiarch and his suicide mission were cut down by the Black Legion (now Sans Bringers of Despair, Falkus Kibre aside) it is most certain he had the smuggest of smiles as he was butchered to death.
When the Carcharodons arrived with the Imperial Navy to back up the nearly extinct Blood Angels and mopped up the remaining Black Legion who were still straggling behind after the main part of the Crusade had packed up and fucked back on to the Eye of Terror--they found an interesting discovery. All the unrecovered Blood Angel corpses had had their gene-seed ruined beyond repair, an insult to unworthy opponents presumably. Of all the Chapter, only a handful of bodies were left undefiled: Reclusiarch Jorus and his Death Company, clad in their battered and broken black ceramite, seated in makeshift thrones made from the Bodies and armor of those Black Legion warriors they had killed on that fateful night.
Pure. Distilled. MotherFuckin' Awesome.
In the same vein as The World Engine. Proof that GW can still write cool stories where all sides, get their time to shine and bloodied in equal measure.