Board Thread:Spoilers!/@comment-27060727-20171014181959/@comment-25375217-20171015021639

I think it's most likely that "The Eighth Witch" refers to things we haven't seen before, not seven old characters that the writers have forgotten but the fans haven't.

I could see it connecting to Zelena and Regina somehow, but more likely it's a completely new backstory for Booth's character.