Progression zone is a design anti-pattern which only allocates specific level range of monsters in the zone, as if the zone was a level in single-player linear RPG.
example: put only monsters level 2-5 in zone X.
1.Dynamic levels: monsters are spawned to suit average player level in the zone(active players).
2.No Levels: monsters and players don't have levels and difficulty progression is very minor if at all.
3.Level-scaling:monsters levels scale up with high-level attackers.
4.Diversity of monsters levels: areas contain many different monsters of wildly different levels.
5.Area adaptation: monsters levels raised if players easily defeat them, lower if zero activity for N days detected.