BoM/TWS Message Forum

So here's a question based on recent chapters. Nothing that's important or I plan on using but they have made me wonder something. If one knew the sigils and what they were doing would it be possible to craft a mind band that works similar to a mask? By that I mean copying minds until it's closed. So say in this current story with Will and Cindy, a mind band that copies both Jenny and Yumi's minds and blends them together much the same way the mask did with their appearances.

I would imagine, if so, that's a trick that'd have to be done by someone with a much better understanding of the book, sigils and magic than anyone at this point in the story would have.