Oneness

Oneness was a state of union with the Force. Usually, when a life-form died, they would become "one with the Force" by becoming a part of the Cosmic Force, which then provided power to the Living Force.

On the mission to return the Nameless to their home on Sophros, Jedi Knight Bell Zettifar achieved the state of oneness in a duel with Marchion Ro. Empowered by the energy and will of the entire galaxy, both the light and dark sides of the Force together burned through him. Embodying every Jedi, including that of his deceased master Loden Greatstorm, Bell used the ability to finally defeat Ro. Jedi Master Avar Kriss also obtained a sense of oneness during her time on the planet, being able to hear and see the entire galaxy, its beings, as well as the past and future if she so wished.

During the Battle of Exegol, Rey achieved the state of oneness when she called on to the spirits of all the departed Jedi. The voices included her former Jedi Master Luke Skywalker, his father Anakin Skywalker, Obi-Wan Kenobi, Yoda, Qui-Gon Jinn, Ahsoka Tano, Mace Windu, Luminara Unduli, Aayla Secura, Kanan Jarrus, and Adi Gallia, who encouraged her and lent her the strength to carry on against the Dark Lord of the Sith Darth Sidious.

Text and facts from the “Oneness” article on Wookieepedia, licensed under CC BY-SA 3.0. Modified for this site.