Each city has a bunker. The bunkers are usually located in a central area in the city. Each bunker has a leader whom the player may challenge. If the player chooses to take the challenge, they will be taken to an instanced arena where they must defeat the leader in a 1v1 battle. If the player is successful, they will receive a pip which is added to the player's HunterBracer. Each leader issues a different styled pip that is unique to their bunker and their city. Receiving a pip signifies that the player is part of the city's volunteer militia. Being part off the volunteer militia will warrent discounts in certain locations within the city, access to certain shops/locations within the city, and experience boosts when defending the city under seige.
The species of monsters, and types that the bunker leader has in their party will always remain the same, but the levels will be modified such that they are always stronger than the player's currently equipped party. Having a higher level party still remains advantageous. The leader's levels will never go below a certain point, so challenging him with very low level monsters will remain nearly impossible. However, as the player's party level increases, the leader's levels increase at a different rate in relation to the player's party such that eventually after a certain level the leader will always remain the same, small level of difficulty above the player.