Forge version: forge-1.12.2-14.23.1.2562
Botania version: Botania r1.10-350
Link to crash log: https://pastebin.com/g0JQsJdd
Steps to reproduce:

1. Just clicked the green Play Button on the Launcher.
2. The forge loading screen starts loading.
3. While in the Pre-inicialization phase 1 or 2......
   What I expected to happen:
   The game should load corectly!
   What happened instead:
   But crashed before the main menun shows up.

Additional information:
I have these Java Arguments in the Launcher:
-Xmx6G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=16M

Yes, it was Chisel. But not because of Chisel itself. Its just because I don't downloaded the new api needed by Chisel for it to work proprely. It is called CTM (Conected Texture Mod). So I downloaded it and...

So, basicly... My game is now working fine.

Hi, I was getting this crash too so I did a remove all mods and add them back in one by one. Turns out it doesn't crash when I remove Chisel. Chisel & Bits is fine just Chisel seems to be causing this crash for me. Have you tried removing just Chisel? Let me know if this works for you too. Might have to report to Chisel.
Edit Okay to compound my confusion. I noticed the ctm mod required by chisel was reading unknown in twitch. I thought maybe if I try to delete ctm and chisel and re-download freshly it may work. That is exactly what happens. It will launch with the fresh ctm and chisel files. I have no idea what happened there. Hopefully this may help with your crash too.