We all got introduced to Salem at the end of the Volume 3 finale. She's obviously the one Cinder's working for. Now I'm not quite sure what the hell she is. Some may say, "She the Queen of the Grimm", but she speaks of the Grimm as if she were apart from them. Oddly enough she looks like she could be a Grimm with a human form. Whatever the case it seems that maybe she's the one masterminding all the scheming from the first three volumes. However I ask people to consider this. In the first episode of Volume 1 it seemed Roman was the main villain until Cinder was shown, just without a clear look at her face. Then we learned who Cinder was at the end of Volume 1.
Personally I was thinking until episode 7 of Volume 3 that Cinder was the real mastermind. Afterwards I heard Cinder explaining she wanted "to be strong" and to be "feared." When in the hell does she explain herself to anyone?
That made me think of how young she still is. Maybe she's human. Maybe she's not. Who the hell knows what she is at this point? By now we've seen what she can do. However it no longer made sense that Cinder was the mastermind. Then a few episodes later Salem shows her face. I was thinking, "So this is the force responsible for turning Vale into a total clusterfuck." At this point that's what it seems like but is she the only being of her kind?
To me there's no way she could be the only one of her kind. There may a whole bunch of beings like her, all dedicated to her goals.