Minecraft 1.12
Forge 14.21.1.2426
AbyssalCraft 1.9.4-pre-4

Crash log
I tried to place a Dreadlands Portal. Since then the game always crashes as soon as I enter the dimension.
I move my player position back to the Overworld with MCEdit and reentered The Wasteland, still crashing.

The stacktrace points to something throwing a NPE in the pathing logic when the EntityAIAttackMelee task is updated. I believe someone has posted a similar crash at some point in the past, but I'm unable to find the issue they opened regarding it.