Monster hexes will occasionally become infected with events called escalations that are invasions from a monster faction, such as a bandit gang moving into the area. Hexes affected by escalations have their base monster populations changed to reflect the escalation. Escalations can grow and infect additional hexes over time.
[However, this game mechanic is at present turned off, probably until player population increases.]
Escalations can be weakened by killing monsters and completing escalation events in the affected hexes. These events require killing monsters, interacting with objects, collecting items, etc.
In December 2018 Goblinworks announced a player event called The Nhur Athemon Sequence, series of increasingly difficult escalations was launched in all standard monster hexes (except Monster Homeland hexes). The sequence of escalations used in this event represents an order of increasing defficulty.