From publisher blurb: In this urban combat encounter built for fourth-level characters, the heroes are on the defensive. Either due to mistakes made by the players or because of the actions of an antagonistic law enforcement organization, this encounter has the adventurers forced to fight off an incursion by an aggressive and well-organized magical tactical response unit. The context of the encounter is up to the game master to decide, however multiple examples are given for them to be able to place it anywhere throughout the campaign.