So they ruled that homeworld when they were the Blood Dragons then. Maybe they had the belief that civilized and refined behavior would counter the Thirst. That's why they got so involved with the civilian populace, they wanted to put on an air of nobility and grace, believing it would keep the animal in them at bay. But it didn't work. The Marquis had a huge palace where he entertained many guests, he was an excellent performer and writer of theatre, played electro-dulcimer and hosted salons for writers and nobles. But in his heart he was being consumed by visions of slaughter. The pretty servant girls that attended to his chambers, how he longed to rip their heads off their spines. The arrogant, pretty nobles that came to his receptions, he would have the most intense impulse to murder them all with their dinner implements and then spread their innards all over the table and feast... He couldn't restrain himself.
And one night, when his urges were unbearable, his party was visited by a strange guest. A woman of unknown lineage, but obviously noble, for what other woman could carry herself so proudly and gracefully? She embodied all that he strove for. Elegance, refinement, civilization. So he pursued her, not for sexual pleasure, but for her calming effect on his secret, shameful urges. Because whenever she was nearby, the Thirst receded in him, the blood calmed itself.
And finally, she revealed her nature to him, and he was overjoyed when she told him of her master and the gifts she could offer, not just to him but to all her brothers...