Adventurer's League

From Cult of the Turtle Wiki

Only those who have spent a year in the Adventurer's League can be Citizens of Haven. There is also a tax to pay to join, but in the end, as a Citizen it is worth it. Also, Haven gets a citizenship of people with adventurer levels, in case they should ever need them as defense.

As such, Haven doesn't have a standing army -- who would be able to attack them anyway, nor a police force -- the Adventurer's League takes care of all those duties.