It appears this mod doesn't like the Artifacts mod very much. Been using Artifacts for multiple months in my pack without problem, and upon installing Smooth Entity Light, Minecraft says both mods have been identified as potential causes.

For reference, I'm using...
Artifacts 1.12.2-1.1.0
Smooth Entity Light-4.0.4-MC1.12.2
Forge-14.23.52487

Here's the log:
crash-2020-11-08_14.55.36-client.txt