Barrier

A is an impermeable membrane of energy, either spiritual or demonic. It can be cast over a wide area, as with Mount Hakurei, or around one person or group of people. Barriers protect the caster from all sorts of dangers in the Feudal Era, such as energy blasts and physical attacks from humans and demons alike; most barriers have the ability to prevent intruders from entering the protected area altogether.

Barriers are commonly used by those with strong spiritual power, such as priestesses and monks. Some demons and hanyō also have the ability to erect barriers. The sheath of Tessaiga also has the ability to create barriers to protect the wielder from powerful attacks.

Naraku in the course of the series makes use of some barriers, to hide or to protect themselves from powerful attacks. Even his incarnations were born after the creation of these barriers can make use of them.

Trivia

 * The colors of the barriers seem to be violet for evil characters, and blue for good characters. It doesn't seem to be based of demonic or spiritual energy, as Tessaiga's barrier is blue and Naraku, Hakudōshi, the Infant and Byakuya's are violet.