You could fake it with a mesh and material which is attached to your character or camera. It would be a kind of fake volumetric effect, like in the weather fx pack on the marketplace.
For the material you would need a cloud texture/mask created in Photoshop or in Substance Designer, than connect it to a panner node to make the clouds move. Than setup everything with the emissive and opacity slots to make it work.
Of course there is a bit more to setup but i think there is good tutorial on youtube for a volumetric fog/light effect.