Forge: 14.23.4.2708
Hardcore Darkness: 2.0
PlayersChoice: 1.2-4

https://gist.github.com/TeetoKaziim/041ea0ed41ae428855315561e18b7b45

How it happens:

Using Player's Choice, define Hardcore darkness as an optional mod in config\playerschoice.json

( Like so: https://gist.github.com/TeetoKaziim/6d6efa26cc9a9dc4229e57a040c9dec3 )

Then, on first launch of the modpack, select to have Hardcore Darkness disabled. The pack will need to restart, and when you load it again, it will get to the main menu just fine. But, when you open a world, you get the crash in the gist at the top of the issue.

Thanks a bunch, and take care.