Board Thread:Speculation House/@comment-14138255-20141031002615/@comment-25555436-20141116230734

Which leads to a small variation of the connection web. If Adam did start the Grimm Mask stuff, and if he did teach Raven, then it would explain her Nevermore mask, even if she wasn't part of the WF.

Then again, she could have teached Adam before he joined the WF. And when he joined, he simply introduced the concept of using grimm masks to the faunus. If so, Raven started the Grimm Mask stuff, her disciple Adam followed it and introduced it to the WF when he joined.