Hey guys, after watching the end of Volume 5 I began thinking and started creating a few theories. It might be long, but please stay with me and let me know what you think (: Contains spoilers, obviously.
I believe it wasn't stated or revealed before this volume, but it appears that the Maidens are the key to the Relics. This would explain why Qrow was sent to find/protect the Fall Maiden in the early volumes, and why the Spring Maiden was so important to both Raven and Qrow.
Now, we also know that Salem is after the Relics, which would mean she needs the Maidens.
First of all, if Cinder is now the Fall Maiden, doesn't that mean she needs to be at Beacon in order to open the gate/portal? Last time we heard, Salem's team had yet found the Relic, which would mean that Cinder needs to be there to open the portal when they do, but she obviously hasn't been there because as we've seen, she'd been through training with Salem and then searched for Raven/the Spring Maiden. Of course, the natural thought would be that she doesn't have to be at Beacon until the Grimm have found the portal, but this is where I'll point out something that I noticed: When Pyrrha died, she turned into a golden hugh and then disintegrated. We saw Vernal's death this season, but when she died her body stayed in tact. I've read a theory somewhere that Cinder has the ability to teleport, which fits this theory: Pyrrha was transported to where Salem is, and, while dead, she's at Beacon searching for the Relic. Now, I say she's dead because Cinder has the Fall Maiden powers now, which only occurs when the previous Maiden dies. But what if she wasn't really dead dead, but like in a similar state as Salem?
Many theories have stated that Salem is the Winter Maiden because of the similarity she bears to the original one. I would have to agree that she is the original Winter Maiden, because how else would she have known about Oz, the Relics, and even have the power to control Grimm? Now, while I do think she is the original Maiden, I don't think she still has the powers. Salem's appearance is clearly not human, and her ability to control Grimm doesn't seem like something anybody can do (otherwise there wouldn't be a problem with Grimm) so what if she's no longer alive/human? Remember in Volume 4 Chapter 1 when team RNJR was fighting a rock-looking Grimm that could use trees as a form of shell? And then, at the end, it turned out to be a Grimm possessing the rock? What if that's the case with Salem, and now Pyrrha, where she is now possessed (or has the soul of a Grimm in her)?
According to this theory, where a Maiden doesn't really need to have the power to open the portal, that would also mean that Salem could already have access to another relic (the one that's associated with the Winter Maiden).
Now that we know that we need the Maidens in order to obtain the relic, why doesn't Salem just go and find all the Maidens (with the help of the Grimm as it's been shown that they're currently searching through Beacon for the relic) to get their power and then open the portal? We saw in this Volume Cinder's desire for the Maidens' power, which is why she attacked Vernal and also tried absorbing Raven's power. While we as viewers don't know if it's possible/what will happen, what if it's not really possible? What if fully having two Maiden's power may result in some big consequences (maybe even death?), which is why Salem doesn't hunt them down, and Salem just isn't telling Cinder because she doesn't care anymore. Salem doesn't really need Cinder anymore if she has Pyrrha.
Anyways, that's all I really have for now. Thanks for reading :-) If someone has already stated something I mentioned, I don't mean to steal ideas, it was not intentional! Let me know what you guys think!