Board Thread:Speculation House/@comment-14138255-20140801004849/@comment-10380701-20140803023756

I assume that anyone living outside the four kingdoms are essentially pretty much living in Fallout, given how supposedly dangerous it is. If that's the case, then being a badass is most likely a common thing if you manage to survive out there.

Menagerie is an example of a proper area outside of the four kingdoms, so it's not entirely impossible that Blake had lived in Menagerie and most likely joined the White Fang there.