Board Thread:Warhammer 40k General Discussion/@comment-64.121.236.162-20140910042956/@comment-72.93.49.215-20140912194128

Yes Neithen I know. But at that point in the heresy their gene seed wasn't tainted yet. It became tainted to the point of basically no return after the entered the Eye of Terror.

However the Night Lords who never did for example still have a very pure gene seed. It is mentioned in this wiki that they could bolster their own legion the old fashion way if they had the facilities and personel, but they don't.