AFAIK, Mercurial's split personalities happened from long term BTL abuse (as well as a few personal tragedies). While it is possible that Sybil originated from BTL code somewhere, I don't think it would be connected to Maria Mercurial, or we would have heard about it a long time go. Afterall, there's been beetleheads in the shadows for decades now, and this is clearly different from anything we've seen to this point. Now, if dissonant sprites got hold of BTL code to try and become inhabitation sprites...