He's quickly drafted in to deal with trouble makers
The Draft Mercenary Guard is a monster that spawns for a certain time when a player attempts to open the Wooden Doors that lead to the Desert Mining Camp. When spawned it will always attack the player, try to remove their keys and get him into jail. He no longer succeeds removing the player keys and getting them into jail upon quest completion.
Due to the guards despawning after a short amount of time, they may not be an attractive way for players to train post-quest unless they have good combat level and armour to assure their kill before the time runs out.