I'm going to pitch this theory on the assumption that you've all never heard of the setting I'm going to describe, since that simplifies things for everyone.

So, the crazy theory is that the setting of RWBY, a planet named Remnant with an inexplicably shattered moon, is a Daemon world in WH40K, or at least a world heavily beset by Chaos. There are entities called the Creatures of Grimm who prey on the human (and abhuman Faunus) inhabitants of the planet, and only them, to the point that human civilisation is at present restricted to four major cities and a few minor villages; these Grimm are, in fact, a localised form of Chaos Daemon, twisted into the shape of black-furred, white-armoured animals by the collective unconscious of the human population, which obviously received free reign to enter realspace and roam the planet after whatever Chaos-based event broke the moon into pieces that didn't then get pulled back to the main body by gravity. Grimm spawn from the Warp, they dissolve back into the Warp when they're killed, and their power and intelligence increases over time because they're gradually becoming more attuned to realspace, or the human collective unconscious is turning them from lesser into greater daemons, or something along those lines. Said collective unconscious also led to the planet not being twisted into an entirely horrific landscape of death, as most (though admittedly not all) Chaos planets are... or maybe the actual breach is on the moon, hence shattering without gravity collapsing it back into a single celestial object, and the Grimm daemons just drop down to the planet from there.

Normally, this would have ended the humans easily, and as RWBY itself tells us, it nearly did. However, two major things (and one minor thing) have let them survive to in-setting modern times. First of all, the presence of so much ambient Chaos energy has led to rampant mutation in the majority of the human population, which inexplicably only manifests as low-level, semi-uniform psychic powers; these are represented by the Aura every human and Faunus (and other normal animals, to a lesser extent) possesses on that planet, and usually also includes a Semblance which is unique or semi-unique to any given individual. These low-level psykers are practically immune to being further mutated by the use of their powers or to other negative effects that might normally occur through use of psychic powers, but suffer for this by not only having limited psychic strength and versatility, but also restricted access to the Warp itself at any given time, thus why Aura depletes as damage is taken and dealt out, and recharges when not in use.

Secondly, Dust, with uses and effects as explained by RWBY. This is a useful resource, and is obviously one of the major reasons the human inhabitants have continued to not die. What it actually is is crystallised psychic energy. More specifically, the four basic types of Dust each indirectly represent one of the four Chaos Gods, who are probably looking at Remnant and giggling like lunatics at the struggles the humans on the planet are going through, since there's no way in the Warp they can win in the long run. The third, minor point is that constant exposure to the Grimm daemons and the aforementioned ambient Warp energy has lessened the collective supernatural fear response of the human inhabitants, such that trained Hunters can readily fight against the Grimm without flinching... though obviously, normal humans are still going to be terrified by a large-scale attack, since normal humans tend to be scared of giant monsters regardless. If it's not obvious by this point, the humans and Faunus have no idea what's really going on - "what is the Warp, what is Chaos, you're a crazy person for worshipping these weird fake "Chaos gods"" - which is in part why they're not all Chaos worshippers on a Chaos planet. The planet's also relatively obscure, and probably contained somewhere in Chaos-held or uncharted space, thus why it hasn't been Exterminatus'd into oblivion or overrun by Chaos Space Marines.

There's a bit more to my theory, but it's very spoiler-ey in nature, so I won't talk about it unless you guys really want to hear it. Other than that, I'm pretty much done. Any questions?