Board Thread:Episode Discussion/@comment-162.157.243.114-20170418161801/@comment-25862208-20170418164745

Right now, I think the answer to that question is very much open to a lot of different theories/possibilities. My first thought was that the Grimm "gene" was a simple genetic mutation that, despite being recessive in nature, was able to stick around, but I also secondarily thought that perhaps Zerstörer's Staff had something to do with creating the first Grimm.