Magic barriers
A magic barrier is a magical field which can prevent certain creatures or all creatures from passing through it. This barrier may do so by scouring whatever attempts to pass through it or by physically impeding whatever tries to move through it. Magical barriers are commonly used by mages to protect their work or contain their experiments. The spells to create and dispel these barriers are closely regulated (especially by the Empire) because they can be easily misused. Barriers may also be assigned special and secret motions which can temporarily dispel a barrier, if a mage needs to move through one constantly. Interestingly, barriers are one magical construct that is much more difficult to dispel than it is to create.
Fire
A fire barrier is a weak field which can easily be pushed through. However, walking through a field of magical power is bound to leave all but the best mages lightly charred. Fire barriers have little to do with actual fire, despite their name; their source of power is purely magical.
The weakest of fire barriers are commonly used by mages to cleanse their bodies of invisible creatures which may be clinging to them. Weaker fire barriers are found in areas where may, for exmple, be developing new types of plants or fungi. They can quietly disintegrate spores or small insects without any trouble to a mage, who would otherwise have to spend precious time hunting down and destroying contaminants to their experiments.
Fire barriers are also used by mages to contain quickfire, as quickfire operates on the same principles as the fire barrier and can be contained by one. However, they are not indestructible. Groups of animals have been known to break down fire barriers completely, making them unreliable for defense or hostile containment.
Force
A force barrier is the ultimate protection against anything but other mages. A force barrier cannot simply be knocked down or burned, as a wall might be. In addition they are impassable. However, a mage can use the proper spell to decompose a force barrier.
Force barriers repel physical objects, unlike fire barriers. For this reason they cannot be walked through or be shaped in any non-magical way. Force barriers can be used to patch damaged walls when no other materials are available. Force barriers are also impervious to quickfire and all types of magic except their dispeling spells. However, while they are impassable, animals have been known to break them down by eroding their links to the earth or walls. Once they are not anchored any longer, they are rendered useless and degrade. For this reason, barriers are normally found anchored to smooth surfaces, such as basalt walls, or under the supervision of a mage, such as at Fort Emerald.
Other
Magic barriers were also used by the Olgai tribe to partition Avernum during the Empire-Avernum War. These barriers were stronger and invulnerable to spells that were normally used to dispel barriers.