There were several dangerous places in Eastern Region publicly acknowledged as No-Man Zones or Forbidden Zones.
Those places all had similar characteristics: they were places where spirit beasts occupied the largest amount of territory and where bizarre things happened.
The Blackwood Forest was certainly one of those Forbidden Zones. The forest was the only place where black-colored trees grew.
Another place that was not the least bizarre was Eastern Wilderland.
There was a saying in Eastern Region, "No matter how much the passage of time, there is still no season in Wilderland."
It was a popular saying, the kind of saying that even a three years-old child knew.
If the children misbehave, their parents must have, at least once, threatened to throw them out to Wilderland. And their children will stop crying and act spoiled.