The Lamenters, commonly known as the Imperium's standard-issue unlucky bastards, the Emperor's pitiful little crybabies, and Sanguinius's door-prying sons.
They were born during the Cursed Founding. Every Chapter created in that Founding shared one distinctive trait: spectacularly bad luck. (It was actually a failed Adeptus Mechanicus experiment to improve gene-seed.)
Their reputation for misfortune made other Chapters unwilling to associate with them. Often, those Chapters ignored their requests for support over Warp communications, making them even unluckier.
They were the Chapter the Sons of Sanguinius had been desperately searching for. To some extent, they had indeed suppressed the Red Thirst and Black Rage, a secret every Blood Angels successor Chapter wanted to learn.
But their earth-shattering bad luck, elusive movements, and tendency to vanish without a trace meant the Blood Angels and their successors had never managed to find them.
Consequently, their tactics and weaponry had virtually nothing to do with the Blood Angels. Their arsenal drew on everyone else's strengths (poverty and scavenging), and they favored close air support, though lately they had grown so poor they barely had any support aircraft or transports left.
Yet as time passed, these poor souls grew unluckier still. After lying dormant for five thousand years, the Red Thirst and Black Rage unique to the Sons of Sanguinius struck the Lamenters with tenfold force. The genetic flaws they had believed cured erupted after five thousand years of constant mutation, catching these warriors completely off guard. They formed a substantial Death Company, one desperately short of Dreadnoughts and Terminators.
At first, these unfortunate warriors had been perfectly normal, campaigning along the Imperium's frontiers. Then, for some unknown reason, the High Lords (humanity's supreme leaders, since Guilliman had not yet awakened) grouped the Lamenters, who were far away on the frontier preparing to relocate, with