Barrier

Barriers (結界) are zones or territories established with jujutsu. They are generally used to conceal, contain, or deny entry to entities within that space. Cursed techniques that erect barriers are known as barrier techniques.

Description
Barriers are territories of various sizes and effects that anyone with enough cursed energy can learn to create. Some barriers, like curtains, have an outer shell to protect the edge while others do not. Complex barriers can be customized with binding vows and talismans, but this takes a certain degree of skill to accomplish effectively. For example, barring certain people from a barrier is complicated to achieve. Barriers only recognize individuals with cursed energy and they completely ignore inanimate objects and buildings.

Domain Barriers
Barriers are the foundation of any domain, whether it be a fully expanded innate domain or a simple domain. An environment can be crafted out of cursed energy within a barrier. If that environment is an innate domain and the barrier is imbued with an innate technique, it is considered a full domain expansion. In other cases, incomplete domains can create or completely change environments within the space of a barrier.

In most cases, the barrier of a complete domain expansion has an enclosed outer shell that is spherical in shape. They are generally reinforced from the inside, making them weak to outside attacks but there are exceptions. The outward appearance of the domain is entirely different in size and scale compared to the domain expanded within. A concrete image is most important when erecting a barrier that creates an artificial environment over real physical space of a different size. Erecting domain barriers of this degree is difficult for even the most gifted sorcerers. Domain barriers in particular typically have set internal and external parameters, including volume and construction speed.

It ordinarily takes time for a sorcerer to discover the precise blend of conditions to establish their own domain barrier. These conditions aren't usually adjusted after being established, especially not every time the barrier is cast. There are exceptions including individuals whose innate techniques expand their domains by default. To compensate, the caster can overlay their barrier with a physical structure as a base to forcibly enclose it. However, the barrier imbued with the user's innate technique will not incorporate a can't-miss attack, arguably the greatest strength of a domain expansion.

Simple domains also use barriers, whether it be to counter other barriers or expand a domain to a small degree. Binding vows and conditions can also be used to customize the space within these barriers as well.

Trivia

 * Translation Note: In English, the word "barrier" implies a defensive wall. However, Kekkai (結界) means a zone, territory, or field with a boundary. An outer wall is merely a component of a barrier and is irrelevant to the literal definition of Kekkai.