My guess is the Tekne. I'm sure they discovered this issue long ago, and is probably why they offered immortality to the Nonmen in the first place. They knew that they could kill all the women, and then wait around for the those that remained to go crazy. They may have been surprised, once again, at the Nonmen's abilities though, and didn't expect them to even semi cognisant after to many thousands of years.
I don't think Mek is important. He's just been all emo, moping around in the woods all alone, depressed after he realized what he helped Shae accomplish.