Just playing with couple asset for bigger scene. I slap stuff on … beveled cube and call it a day smiley
For stone I use as base free Sketchfab model Rhynie 6 Pictish Symbol Stone" (https://skfb.ly/op6XE) by Douglas Ledingham I cut it, and resculpt in ZBrus, make ne textures. Thingy above stone is just one old hard surface practice from C4D. Cycles 1024 samples. I try with real volume scattering… but even with 1024 samples ( and loooong render time ), there was loot of noise. Denoiser do good job with noise… but also do very bad job with details need better GPU for this kind of stuff.
If first picture from your post ddoesnt have volume scatter, did you use particle emitter with smoke screen png? Also as a fellow scene person, it has real doom vibe thanks to the runes, maybe some red and purple lighting would give it more of a fire and hell vibe which i think the picture would definitely gain more personality from other than that good sh*t.
Oh nothing so complicated, I just cheat
I use mist, Z depth, emission pass also in workbench I render masks. Rest is Photoshop. It’s tricky to get volumetric in this way, especially when you do fast, dirt job. But this is more or less just fun, something I do for my …pleasure.
I never go further form this test. Render time was terrible with too much noise. On the other hand, I was to lazy to switch to Octane which are faster with volume scattering. Octane is nice, but I love Cycles more… shader setting is much faster easier to me in Cycles.
need better GPU for this kind of stuff. 
other than that good sh*t.