Religion

Personally, I've always been a fan of the "No Animosity in the Afterlife" trope.

When a character dies, with rare exceptions, they end up in an afterlife populated by other deceased. Some of these people will have been friends or loved ones in the living world, reunited at last. Some of these people...well, let's just say not everyone in Heaven was on good terms before they died. Some of them were even bitter enemies!

But in the afterlife, there's little reason to care about former rivalries and disagreements. It stops mattering what happened when you were alive, and so the people you used to hate, suddenly, aren't so bad at all.

This may happen because the afterlife brings a sensation of peace and understanding. A character once consumed by rage or jealousy or power can gain some perspective after death, and become a much calmer, friendlier person. At the same time, there's nothing left to pick a fight over, anyway. You don't need money, land, or authority when you're a ghost— so why continue to hate the people that challenged you? With the entire reason for the animosity being nullified, rivalries can be put aside. However, it doesn't have to happen instantaneously. The afterlife is supposed to be eternal, after all. There's more than enough time to mend bridges with the people you used to fight with, so some works portray this process as being about a gradual bonding and forgiveness process while there's nothing left to do but talk to each other, rather than an immediate shift.

Having this occur between individuals is most common, but it could also happen on a larger scale. Entire warring nations could become friends in the afterlife, and though their descendants will still fight, at least the afterlife brings them a truce.

Now this is just me forcing the two legends to work together and is by no means cannonical.  I came up with this for my own fanfiction because I get stuck writing if there's a huge plot hole glaring right at me. Now, I do not claim that this is a 100% fit and for all I know it could have its own gaps in reasoning, but to me at least, it sounds more coherent.

Also, let's just go with the assumption that faunus and humans simply fall into man/man-kind/humanity okay? It keeps things simple.

You're free to use it as you wish and I just thought of putting it here for anyone to use. If anyone see's any faults to it, you're free to dismiss this entirely. 

When the two brother gods decided to work together to create man, the first they created were name(for simplicity's sake) Ozpin and Salem, who both wielded great power. The two gods saw that their work was good, but they were too good, so they continued working on the rest of humanity while taking steps in leaving Remnant, assured that their creation would come out perfect. Now, the Ancient Grimm still roamed Remnant and gods tasked Ozpin and Salem with eradicating them while they were preoccupied.

As Ozpin and Salem continued their task, one Grimm evovled more than others. He called himself Eblis(named after the fallen angel that courted Lilith in the Sumerian/Babylonian legend) and (you guessed it) wooed Salem. She fell in love with the Ancient Grimm and Salem became the mother of the modern Grimm we now see in Remnant. The two gods notice this and are angered. However, due to them having taken steps to leave Remnant, their power was limited to taking away most of Salem's original power and then tasked Ozpin to destroy her along with Grimm.

Ozpin is succesful in destroying the Ancient Grimm(along with Eblis) but hesitates once he came face to face with Salem, who he had loved. Salem then took that chance to escape, along with the life of her beast-like Grimm children. The two gods frown at this result but could no longer change their departure. They charge Ozpin with continuing his work of defeating Salem and her children while they leave Remnant for good.

For a time, Ozpin continued his task of searching and hunting down Salem and her children. Due to his lingering affection for Salem, Ozpin grows bitter and callous, believing his task to be a curse from the gods. Eons pass, and the four maidens come along. Just like the legend, the maidens teach Ozpin to make peace with himself and open his eyes to world, and especially to humanity and just how far they had come. This leads to Ozpin making peace with his task and makes plans to set out and end Salem once and for all.

Before he could, however, Salem springs her own attack, targetting huamnity while she keeps Ozpin occupied. (Alternatively, she recognizes Ozpin's love for her and rekindles her love for him. She locks herself in some sort of prison-dimension with Ozpin to prevent him from interfering with her plans and tries to tempt him to join her). Unfortunately for Salem, Ozpin has already made up his mind to complete the two gods' task for him and he surrenders his power to the four maidens, who were succesful in pushing the Grimm back. In anger, she kills Ozpin but he quickly reincarnates due to the two gods' task.

Ozpin then tries to rally humanity along with the four maidens to eradicate the Grimm. Salem recognizes that an all out attack would no longer work for her and switches tactics to subterfuge and sabotage. This leads to humanity hungering for the four maiden's power and human race is quick to fall. Recognizing this weakness, Ozpin then turns the four maidens into legend and still tries to rally humanity to defeat the Grimm.

This is now leads to the stalemate between Ozpin and Salem at the very start of the series.

P.S. 

As for the relics, until they show that they're some kind of power, I just go by the assumption that they are just PHYSICAL MANIFESTATIONS of humanity/Remnant. In other words, if you destroy these, you destroy the anchors that keep humanity or Remnant from spontaneously combusting to their constituent atoms. 

P.P.S

Salem does not control on a global scale. They do, however, listen to her the same way a child would to their mother.

So I've been trying to puzzle something out for a while and I still can't figure it out. So as Qrow and Ozpin would tell it Humans were created by the Brothers to be the only beings able to choose their own fate...so where the hell do Faunus work themselves into that equation, especially when Qrow stated in their WoR that Faunus might actually have been on Remnant longer than Humanity...so who made them? Were they the God of Creations children that might have instigated the God of Destructions making of the Grimm, as a form of cruel mockery? Also I doubt he would have made the Grimm solely to just kill animals...after all animals can't truly feel despair or hatred.  But of course that thinking also makes their ability to choose to be good or evil also raises many, many, many questions. So thoughts and theories would be appreciated.