Copying from
a post on reddit:
Hello! I've been playing Regrowth recently, and got to a point when I was to enter Witchery's spirit world in order to progress. I did the usual dumping all my items into a chest (Though I now realize that I forgot my armour and bobbles- Botania Terrasteel, and the mana-storing ring, if it's relevant.)
Anyway, I entered the world, and I noticed that it was taking a very long time to load the world. Then it froze, and crashed. The first crash gave me an empty crash long, but
this is what I got the second time I loaded up my world, and I knew I was in the spirit world. I believe I entered during a nightmare, if that's important.
I'm running Regrowth 7.4, on Windows 10. Witchery version is 0.23.2. I have also added Optifine and the GLSL shader mod, though I'm only increasing the resolution or whatever it's called with the shader mod. (So that things far away don't have crappy lines along the edges, if that makes sense.) I'm using MultiMC as my launcher.
I've tried increasing the available ram for Minecraft from a maximum of 3 GB to 4 GB, but that doesn't seem to fix it. I also notices that when I was in the spirit world, and the game had frozen, that it was maxing out all four cores of my cpu (i5 4690) and was using ~3500 MB or ram. (At one point it was about a GB more than that, but not for long.)
I'm not sure if there's any more information I can think of, but any help would be greatly appreciated!