You need to keep every region free from total corruption to get this. A region gets fully corrupted when the three squares on the region go from empty to filled. To avoid this pick your battles. If you have a choice of two areas to fight in, one has no 1/3 and one has 0/3 pick the first one.
The sooner you pursue this in the game the better. The fastest way to get this is to build a sagewright's guild fairly early on on the increased research area and keep it filled with fairly high intuition heroes. As a warning you may not want to fill it up right away and don't put your best heroes in as they're useful for passing on your bloodline.
After that just make sure to build on every spot. I'd recommend one crucible, two sagewright's and the rest keeps. (if you're playing on normal, I can't speak for Brutal yet!)