Monsters are non-playable characters (NPCs) and fulfill the role of PvM antagonists. Each Monster has unique behavior which consists of both player and monster skills. Monster skills cannot be learned by players, but may be cast through item effects.

Monsters exhibit different skill mechanics relative to players, including:

• Monster skill cast times and delays are fixed and cannot be modified,
• Monster skill range is rectangular and is not reduced by elevation differences,
• Monsters are not subjected to skill prerequisites or catalysts,
• Monsters may be subjected to skill specific errata, and
• Monsters may use skills at a level naturally unattainable by players.

Monsters are generated through dynamic, and static, spawns. Dynamic monsters are generated within a predefined area on a given map. When a dynamic monster is defeated, it is regenerated within an area on the same map as defined by its regeneration timer. If this area is undefined, it may regenerate anywhere on the map excluding 15 cells from the map edges. If the area is defined, it cannot regenerate within 4 cells of the South & West and 5 cells of the North & East edges respectively. Static spawns are governed by NPC scripts and are not subjected to the aforementioned rules.