Describe the bug
Crash while generating chunks

To Reproduce
As described here: Potion-Studios/BYG#301 (comment)
I'm unsure if it is caused by eidolon or BYG

Environment
forge-1.16.5-36.0.15
byg-1.1.10.jar
curios-forge-1.16.5-4.0.4.0.jar (required by eidolon)
eidolon-0.2.7.jar
Xaeros_Minimap_21.3.0.2_Forge_1.16.5.jar
XaerosWorldMap_1.12.0.2_Forge_1.16.5.jar

Crash Report
https://gist.github.com/MatthiasMann/821fabc68497a233f4eec1acbf9801a7

Hmmm...nothing in the log indicates Eidolon as a cause. My guess is that it's BYG? But it's hard to say for sure. How often does this crash happen, and can you try with or without Eidolon to see if the error persists?

I only had the mods listed installed - and it happens every time I come into a specific chunk.
Without Eidolon there is no crash - and with Biomes O Plenty instead of BYG there was also no crash.
So it's just the combination of these 2.

Something I saw referenced in a similar stack trace (so not the same and older MC version) mentioned something about the biome specific spawn list being empty?
I think Eidolon is placing mob spawners in it's underground structures - could it be that they get an empty list somehow?

Ive got no clue either