From Gamesverse Wiki
A Dimensional Barrier is a spell created by the Al-Hazredians which creates a bubble of space that is an approximate recreation of a given area of real space, offset into the Dimensional Sea. When the spell is cast, most non-magical and non-animate matter within the area is roughly duplicated in the newly created bubble; animals and plants are sorted by their magical capacity, with those having above a certain level being pulled into the bubble of space, while those below that level are left in the original area. Objects with strong inherent magic of their own are also pulled into the altered space.
Those pulled into the space cannot exit it until the spell is ended or the barrier is forcibly broken. Sufficient magical force directed at the edge of the bubble will disrupt it and drop the parts of its contents which were not created by the spell back into the corresponding area of real space. The same effect occurs when the spell is ended normally. It is possible, but difficult, to exit the bubble without disrupting it after it is cast.
The spell is commonly used by at least one combatant in an anticipated magical conflict, in order to exclude bystanders with sufficiently low magic levels and prevent undue collateral damage to the area--damage done to the recreated matter within the bubble does not transfer itself back to the original objects in the corresponding area of real space. It can also be used to contain mages and prevent them from escaping, though they can attempt to break the bubble via brute force from within.