User blog comment:Primarch11/Guilliman Heresy/@comment-3245042-20120615152958/@comment-2253300-20120615160225

That's true, but one way or anther these three issues would lead either to the Legion's destruction or corruption. It might not be as sudden as when they lost Prospero, but they would subtly end up corrupted, or all at once given that they needed Tzeentch to hold back the Flesh Change.