Perhaps those that practice elemental magic begin to take on characteristics associated with their chosen element. For instance, an earth elementalist might be prone to agoraphobia, while air and possibly fire elementalists might have problems with claustrophobia. Water elementalists might always seek the path of least resistance. A fire elementalist might have a cat's opinion of water. This could also apply to physical differences. Fire elementalists might have a freakishly high metabolism and a permanently high body temperature. Water elementalists would probably never get dehydrated, but might slow down a lot when it's cold. Etc, etc.
In cases where a person has accused another of a crime, but there are no other supporters of the accusation or defenders of the accused, and there is not enough evidence to support one party or the other, the two people involved, or their champions in some cases, must duel in the presence of the local ruler or leader. The loser is assumed to be lying and punished accordingly.
It is not considered a crime if a ship's crew mutinies against a captain that is obviously unfit for the post (dangerously incompetent, insane, or overly cruel). Assuming, of course, that they can prove it.
Rivers and other natural boundaries are used as political boundaries as well.
In addition to the Thieves' Guilds, there is a hierarchy that all thieves are part of. Rank is based on skill, and can be raised or lowered at any time. The Queen of Thieves, the greatest living thief in the world, is the ruler. Guildmasters answer only to her, and she answers to no one at all.
The members of the party has unknowingly been infected by a mysterious plague and have been spreading the virus for quite some time now while adventuring. They start to hear rumors of all the cities in quarantine after they travelled trough. Will they discover the source of this? Will people start to avoid them, try to kill them?