The source code for Subterranean Wilderness, a spiritual successor to WTF's CaveBiomes that aims to spice up the old vanilla caves you got bored of years ago and bring you the cave update you always wanted.
tetra's structures only spawn in cold biomes and even then this crash is not guranteed making it not entirely consistent to reproduce, but it does seem to happen and i managed to do it in a clean instance with:
I am having this same issue. My crash reports mention "tetra:feature" and SubWild's spleleotherms. The thread about eidolon might be discussing an issue with the same cause.
tetra's structures only spawn in cold biomes and even then this crash is not guranteed making it not entirely consistent to reproduce, but it does seem to happen and i managed to do it in a clean instance with:
subwild: 1.16.3-1.0 tetra: 1.16.3-3.1.0 mgui: 1.16.3-3.1.2
crash report