These words are also for beginners:
Part A: Hidden Difficulty 1
Part A: Expansive Difficulty 2
The highest level of difficulty for an area
is Difficulty 5. Though even if you use the
words with same difficulty, the type of
enemies varies among the servers.
Highest enemy in Δ server is Level 20.
In θ server, the highest is Level 30.
It's not well known, but areas are divided
into 6 elements: Earth, Water, Fire, Wood,
Thunder, and Darkness.
The type of monsters and items and rate of
appearance depends on these Area Elements.
AFAIK:
Element: Field Type
Earth: Wasteland (Stone walls)
Water: Snow Field
Fire: Desert, Magma
Wood: Jungle, Grasslands, Humus (mushrooms)
Thunder: There's thunder and lightning
Darkness: Swamp (Skeletons)
It might be slightly off, but I think it's
something like this.