Lugft Huron
Lugft Huron (pronounce Lüg-ft Hú-ron) was the Chapter Master of the Astral Claws Chapter of the Imperial Space Marines. He led his Chapter in the defense of the perimeter of the Maelstrom warp storm, but when rebellion festered in the systems he was defending, he decided to take control and put his Marines in charge of things. Thus, the Astral Claws became the rulers of the Badab Sector, with Huron himself as the Tyrant of Badab.
While he succeeded in maintaining order (grimdark though his methods were), his requests to the High Lords of Terra for increased resources to consolidate his gains were denied, and so he decided that, in the absence of help from the Imperium, he would secede and run things his own way. He refused to hand his gene-seed tithes to the Adeptus Mechanicus, and he blocked trade to and from his Sector in order to keep the gathered resources for his militaries. Eventually, he attracted the attention of the Inquisition, and when he blew them off, they decided that they needed to remind him who answered to whom. Thus, the Badab War was launched.
In the end, Huron's rebellion was crushed by the forces of the Imperium, as something like a dozen Space Marine Chapters responded. Of course, Huron wasn't just a rebel, he turned out to be a heretic, and he fled with the last of his forces into the Maelstrom. He is now known as Huron Blackheart, and those forces remaining under his command call themselves Red Corsairs. By the end of M41, Huron is the second most powerful Chaos Lord in the galaxy after Abaddon himself.