I've finally gotten around to messing around with the world builder. I tried deleting the Khadi but the crash still happens. I tried stopping a Chosen of Esus ritual but I'm not sure how, short of deleting a Sidar city, which I will try next. I've noticed that the crash always occurs during a certain sound effect but I have no idea what the sound effect represents. It's hard to describe in words but it's a single tone followed by some whispy sounds, then the game crashes.
Those might be the barbs sound, do you see a Huge eagle, a giant spider or giant lizards? Try deleting them. There are few other that cast spells like the elks and wild men.