I was thinking about this concept yesterday, and I love it! I actually made this post specifically because the purpose of the Mask of Time did not make sense to me, but this does.
@IllustriousVar @Jon @Eljay @Mesonak: You might want to see this. This could add on to that Lovecraftian vibe!
Edit: Although, I’m not sure if she should be all-powerful. That would imply she cannot be defeated by any means. Since she does not have possession of the mask right now, it can be assumed she has either been chased off, imprisoned, or killed.
Edit 2: Also, since she would be the only sister, she’s not the 4th sister.