The Great Plan was a shelter for refugees that was located inside the Caverns of Forever, a set of inter-connected caverns on the planet Cularin that could be accessed from beneath the ch'hala Heart Tree. The roots of the ch'hala surrounded the caverns and the refuge, filling them with the life force of all the ch'hala trees that grew on Cularin, which concealed through the Force anyone who was present inside the shelter. The Great Plan was kept secret by Mother Dariana, the leader of the Tarasin Hiironi irstat, who intended for the shelter to serve as a refuge for the Tarasin, and she planned to reveal the shelter to her people only as a last resort, to keep them safe. However, during the Clone Wars Dariana and her acquaintance Jedi Master Lanius Qel-Bertuk foresaw that a dark storm was set to decend onto the galaxy, and they planned to make the refuge available to the Jedi of the Almas Academy and anyone else who sought to hide from the forces of evil and the dark side of the Force.
In about 19 BBY, Qel-Bertuk sacrificed himself to prevent the Heart Tree from being turned to the dark side of the Force by the Wyrd, a group of Tarasin witches. Following his death, Dariana led the Heroes of Cularin, a group of freelance agents that had assisted Qel-Bertuk during his fight, into the Great Plan, to show them why it was important that the Heart Tree be protected and to offer them refuge there if they ever needed a place to hide.