Using a minimal combination of the mods listed below leads to a crash during startup that appears to caused by Forgelin. (If I am wrong, then please tell me so so that I may redirect the issue to the main cause thereof.) Removing any of these mods along with its dependencies (if it has any) allows the game to start properly. Each of these mods is a latest release.

• AutoRegLib (1.3-32)
• Ender IO (1.12-2-5.1.52)
• EnderCore (1.12.2-0.5.73)
• Ex Nihilo Omnia (1.12.2-0.0.2)
• LibrarianLib (1.12.2-4.19.2)
• Mantle (1.12-1.3.3.55)
• Psi (r1.1-77)
• Random PSIdeas (2.4.2)
• Shadowfacts' Forgelin (1.8.4)
• Tinkers Construct (1.12.2-2.12.0.157)

Forge version: 14.23.5.2847
link to crash log