As DM activity is not something guaranteed, I think we should move towards shifting more creative power in the hands of A/MPCs. One way I've suggested in the past was to allow them to spawn in certain visual effects on top of themselves. This would lessen the need for a DM for storytelling elements and atmosphere and better allow for A/MPCs to take the reigns.
The following effects I think could really add to the amount of atmosphere:
- Mist clouds (red and normal)
- Darkness puddles (that don't actually cause darkness)
- Ritual circles (any of them, glowing and not)
- Blood puddles
If there are more that exist, I'm drawing a blank.
These effects could have a certain length of time they last so that they don't persist too long. They could have constraints placed on them, like maybe one or two active effects at once, so that they aren't spammed. These effects could be spawned in through commands that are enabled with the A/MPC templates, for example @vfx redmist