
Despite this, the Avatar is able to use energybending when in the Spirit World, even when they did not enter through a portal, as they are connected to all the spiritual energy when in that world. Individuals who cross over to the Spirit World cannot use their bending unless they have entered physically through the spirit portals. From day to day, the barrier is weakest at twilight, when spiritual activity is at its highest.

Annually, the barrier between the Spirit World and the physical world is weakest during the summer and winter solstices, which made it easier for inhabitants of both worlds to cross over. Additionally, some powerful spirits possessed the ability to create passages between the two worlds while the portals were closed.

Various locations in the physical world also act as bridges to the Spirit World, such as the Spirit Oasis in the North Pole and the Forgetful Valley outside the Fire Nation village of Hira'a, and are often revered by the cultures living near them.

Other than physically crossing through a portal, there are only a few known ways for humans other than the Avatar to enter into the Spirit World: they can be carried in by a spirit as the entity shifts between the worlds, and certain individuals can cross over through meditation. Jinora was able to guide Korra into the Spirit World through meditation. After Avatar Korra reopened the portals in 171 AG, travel between the two worlds became much easier, as people and spirits could once again physically cross into the other world.

By the same token, only a handful of spirits were capable of assuming physical forms in the mortal world, and doing so required them to give up their immortality. It was extremely difficult for any human other than the Avatar, who was the bridge between the two worlds, to enter the Spirit World, and even then could only their spirit cross over. Prior to 171 AG and the reopening of the Northern and Southern spirit portals, travel between the physical and Spirit Worlds was very rare. Relation to the physical world See also: Spirit-mortal transcendence
