The Fog Bank in Stealing Creation is used to avoid enemies. It can be used by simply clicking in it, making pickpocketing easier as well as avoiding enemy attacks. Also, if you are at the edge of a fog bank then players in the fog can pickpocket you, and likewise if they have selected 'pickpocket' as the player ran into the fog. Most of the time, this fails, but it has its share of success'. This tactic is very common and should be used if the player: A) is gathering supplies and is nowhere near a barrier or home base. B) if under attack or being pickpocketed several times by the enemy. Or C) if the player is low-levelled and is doing either A or B.
This bank can be useful to the player's team and harmful to the enemy. Be cautious though, as you cannot attack, pickpocket, or follow others in the fog bank (aside from the exceptions listed above). It is very useful for getting away from Ancient mages.