There is a mod incompatibility with Thut's Elevators and Colossal Chests for Minecraft 1.12. I've submitted the crash report with Rubensworks on their GitHub. Rubenswork suggested that I should also report this issue here as well - modified with updated information:

Minecraft Version: 1.12.0
Forge Version: xxx.2387
Colossal Chests Version: 1.6.2
Cyclops Core Version: 0.10.7
Thut's Elevators Version: 6.0.0.b
ThutCore Version: 5.0.1
Crash Report: https://paste.ee/p/2Mkfw

Issue:
Minecraft fails to load properly and crashes out.

Details (Modified):
The crash report is not very descriptive; however, when building a 1.12 modpack I had been adding mods 1x1. Issue first presented itself after I had already installed Thut's Elevators and subsequently added Colossal Chests. Testing showed that both mods will work independent of each other; however, when both are enabled Minecraft will crash on load.

Hmm, I will look into it, I will try to get this crash to occur without any core mods* installed, then I will see if I can get it to occur in my development environment, I suspect either I, or Colossal Chests is probably registering something at the wrong time, but it could be something else.

I will go through my registration stuff and see if I can find anything out of order.

*Actual core mods, rather than libs like thutcore and cyclops core

i confirmed that this crash occurs without any core mods installed, I will try to look and see what I do differently between thuttech and pokecube, since pokecube doesn't crash with Colossal Chests.

uploaded 6.0.1 which fixes this issue.