Ok, I understand this book is mostly about steeping yourself in the dark powers granted by the worship of the Dark Gods. That said Hereteks have so many non chaotic options to still have been cast out of the Mechanicus without ever uttering a single prayer or devoting a single deed to any of the Four Gods of Chaos. Xenos tech, unhallowed archeotech designs, Artificial Intelligence, immortality, attempting to clone the Emperor or even just coming to the belief that no complete STC exists anymore and that Mankind must reacquire its lost knowledge itself having gained the wisdom from it previous mistakes to cotnrol that power.
So how would you hand such a Heretek in the ranks of Chaos worshippers? They could still have aligning goals in the short term. He needs their resources, they need his knowledge and ability to turn the greatest weapons of the Imperium against it. Especially valuable would be a Heretek trying to crack the secret of creating a Primarch from scratch to create his own Astrates legions.
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