A split occurs on Mars: part of the Mechanicum’s adherents, including the Supreme General-Fabricator, side with the Warmaster Horus, purchasing that support by lifting the prohibition on researching and using forbidden technologies.
And then the Mechanicum’s joking aphorism—“Knowledge is power; beware of it”—will stop being a joke, and the red planet will plunge into the flames of civil war using the most advanced technologies, including those that are, at first, not subject to humankind at all.