Hi, I downloaded Pandoras Box version 2.1.6.1-1.12.jar and IvToolKit version 1.3.3-1.12.jar and the latest recommended version of Forge ( 1.12 - 14.21.1.2387) and I started up my Minecraft, but when I tried to generate a new world, it just got stuck showing "Loading World" "Building terrain".
I had to manually stop Minecraft and here is what it shows on the Game Output:

New Text Document.txt