The reincarnation cycle can only be broken if the Avatar is killed while in the Avatar State, Raava is removed from the Avatar and destroyed, or the Avatar Spirit is compromised by a spiritual infection.

As part spirit, the Avatar possesses an innate connection to the Spirit World and is at their strongest in that realm, due to being surrounded by spiritual energy.

By feeling all these emotions, it helps you understand how precious human life is, so you will do anything to protect it." The Avatar, formed initially when Wan permanently fused with Raava during the Harmonic Convergence of 9,829 BG, is the human embodiment of light and peace through the connection with the Avatar Spirit.

Returning to the Spirit World, Korra and Raava used the spiritual energy from the overlap of the spirit portals to fuse, seconds before the end of Harmonic Convergence.

Although her Avatar Spirit had returned to her, Korra could no longer connect with her past lives.

The Avatar used that connection to the Spirit World to be the bridge between the two worlds in order to keep peace between them and ensure harmony.

After the Harmonic Convergence in 171 AG, however, Avatar Korra left the spirit portals open and renounced her role as the bridge between the two worlds to let humans and spirits live together in harmony.

After he sealed away the dark spirit in the Tree of Time, Wan oversaw the departure of the spirits to their own world and closed the two portals to the Spirit World, so that no human would be able to physically travel there and risk Vaatu's escape.

Wan took on the task of being the bridge between the two worlds, maintaining balance and peace.

He later used it to end Yakone's reign of terror in Republic City by stripping him of his waterbending.

Korra was also taught this ability after connecting with Aang when she lost her bending.

"The Avatar must be compassionate towards all people, and the only way to do that is to live with them.