The Main Problem
Dungeons.
These were esoteric flora phenomena where flora species, having come into contact with some truly special esoteric substances and absorbed them, mutated in a way that altered the entire landscape, leading to an extremely perilous region.
The mutated flora was extremely sensitive to threat levels, attacking anything sufficiently threatening enough before it could even get close. Thus, only Martial Artists below a specific degree of power could enter and clear the dungeon.
These esoteric flora phenomena were extremely attractive to humankind, for they were ripe with valuable and rare bounties.
Each dungeon was unique.
They usually had characteristics and traits that matched with that of the esoteric substances that they had absorbed from deep underground mines.