OH!!! I thought I had read it was 18 thanks so much!

The Unnatural Preservation ability isn't showing up for me at all and I'm wondering if there's something I'm supposed to do? Or is this a bug that could get sorted out? I'm lvl 27 and looking into my skill tree stuff, I have the abilities that enhance the ability, which is honestly the only reason I even realized I was supposed to have it at all...