Instances can be thought of as private copies of an area and are primarily used to manage resource conflicts. Instances are only created when a player or group first enters the area, and are only destroyed after it has unoccupied for a set amount of time, usually approximately thirty minutes. Generally mobs and object inside an instance do repop, unless the builder has added special procedures. Instances can behave very differently to normal areas, one example of this is that it is impossible to use scry spells to determine what is inside. The marking of instances are a design decision, taken between dentin and the builders. Towns and cities are generally not made instances. Sometimes newly opened areas will be temporarily made instances, to manage an initial high player usage.