I also agree that creatures running up or off cliffs you cant follow is prob the worst thing ever... Is there a way to "not prevent" but give them a bonus to choosing to go any direction that doesn't have elevation of x? OR you could have it so that if someone is "chasing" it or rather its in combat or agro over x than it can't run up or down elevation difference of x.. this would mean you COULD trap chase them in combat, but they could still go over cliffs for migration if they are not in combat... wouldn't that solve both problems?