He was turned against his will.
He feels loyalty to his people and will not feed upon them.
He has endured great pain and in the throes of it, lost himself to the monster inside, slaughtering innocents and feeling guilt for his weakness.
He has worked to atone by feeding only on monsters and criminals (both man and beast).
He has tried to manipulate circumstances to protect his people both from external threats and his fellow creatures of the night.
Despite his opposition to the court he serves and the damage it causes, he still remains at the forefront of its defense.
His name is Abhorash. Heinrich could not help but see the parallels as he read the history of the knight that had served as their Curator. And this Abhorash had freed himself from the Thirst. And he fought alongside the knights of Bretonnia instead of against them.
Thinking back to the others squabbling for control, bargaining with monsters and devils and dividing up the world amongst themselves after a victory they had yet to win and resisted working together to win in the first place Heinrich began to consider finding his way to Bretonnia as well and abandoning the selfish self-destructive despots he was surrounded with to their fates. What was the alternative? Travel the planes to allow a creature of absolute evil to consume another in the hopes of becoming the earthly host of incarnation of undeath? Resurrect the foul originator of necromancy so he could resurrect the demon prince of undeath to again give host to the blasphemy Atropus? Which horrid demon god of death and destruction was most preferable to the legions of Chaos destroying the world and returning it to the Abyss? Perhaps an age of rot and worms and defilement.
Heinrich had never been a religious man, but now he had stood amongst gods and held pacts with primordials. So he was forced to wonder, where was Sigmar? Where was Morr? Shallya? Rhya? If the gods of Chaos and evil were real, then where in all the Hells were the patrons good little Imperials made their supplications to? Where was the alternative to dooming every living creature in the world to either destruction or slavery to the forces of the dead? Once again Heinrich considered disappearing into the night and making his way after Abhorash. Ziegfried was happy, that debt was paid. Rollo had his war, the respect and support of Mannfred, his Templar. Wealdmaer was an evil monster that wished to perpetuate the cycle of evil tyranny that birthed him. And the Dread Master cared nothing for anything but his own personal power and bringing about his version of the end of the world.