Kingdom Hearts χ
As per her role, Ava assembled the Dandelions and trained them in a secret location to prepare them for the travel to the world outside when the Keyblade War broke out so that they could ensure the survival of light.
Five individuals were chosen by the Master of Masters to succeed the Foretellers after the Keyblade War; though only one of them would receive a copy of the Book of Prophecies, and they would be the only ones permitted to remember the world the Dandelions left behind. Ephemer was the first to be approached by Ava when his curiosity lead him to seek answers about the world. Ephemer then reached out to Skuld so that she would follow the same path as him and join the Dandelions, with Skuld destined to become one of the new Union leaders. Strelitzia was the final Dandelion to be approached by Ava, but in trying to convince Player to join the Dandelions. But she was eliminated by an unknown individual, who then stole her rulebook and took her place as Union leader. Brain, Ventus, and Lauriam would later gather in the Keyblade Graveyard as the new Union leaders, though it is unclear which of them is the impostor.
With a Union χ instituted, the Dandelions would be allowed to work with one another, regardless which Union they were loyal to, to continue maintaining the balance by collecting Lux.
Kingdom Hearts Union χ Cross
After the war to celebrate their new status, Ephemer and the others give the Dandelions were given new companions to help them fight against the nightmares. Continuing to follow Ava's instructions, Ephemer considers what to do about organizing the Shift Pride, which would pit the Dandelions against one another as a competition. Lauriam unintentionally inspires Ephemer to consider an alternative, but before progressing, they hold a vote, with Ephemer, Lauriam, and Brain being in favor of the Shift Pride, while Ventus and Skuld oppose it. Ephemer reveals his intention to access the data of the Dandelions recorded through their adventures across the worlds rather than having them fight each other personally.
While discussing the Shift Pride, the others wondered who Lauriam could be looking for, upon meeting Elrena, he asked for her help in looking for his sister Strelitzia. While trying to look for his sister and with the help of the others, they learned that Strelitzia didn't get caught in the war but instead she was trying to save someone from it. Their peace was interrupted when the Darklings and glitches appear all over Daybreak Town, after exploring the new world, the Dandelions discovered they're all trapped in a digital Daybreak Town but Brain promised to get them out. However that wasn't their only problem through Brain's deductive reasoning, they figure out Strelitzia going missing was not apart of Master Ava's plan, he brings Ephemer, Skuld and Ventus to a meeting where Brain explains that he wasn't suppose to receive the Book of Prophecies and it was Strelitzia. He also asks them, who told them about becoming Union Leaders and where, they answer that both were picked by Master Ava but realized that Ventus' encounter was different that's when he revealed a list that had the supposed names. To everyone's surprise, Ventus' name wasn't on the list making him the imposter.
Aware that Ava didn't plan this Brain figured out that Darkness was responsible, he pushed Ventus into remember his encounter with her. He recalls meeting the master in an abandoned house and leaving together but was plagued by seeing an image of Strelitzia dying on the floor. They all decide to return to the clock tower and tell Lauriam what happened to his sister as that went on unknown to them, a Darkness entity led Maleficient through the town to the lifeboat inside the tower, despite Lauriam's best efforts he laid defeated as Maleficient escaped. As Ventus was put to rest, the others were left with more questions than answers despite knowing that Darkness was inside him, they didn't know what it wanted or why it swapped the leaders but they come to the conclusion that Darkness may have gotten her. In his dreams, Ventus remembered what happened the Darkness used him to destroy their comrade and stole her position waking up he was horrified to tears at what happened to Strelitzia. Soon the trio's conversation was interrupted by a grief stricken and hurt Lauriam who demanded answers, then Ventus returns admitting what he had done despite the others' protest. The grief and anger combined caused Ventus to collapse and the Darkness entity to appear making itself known to the others.
While communicating with it, the Union Leaders discover the truth that the Darkness played on Ventus' hidden desire for power despite them believing that Ventus would never resort to such means. That he was suppose to be "the fated child" to harbor the Darkness as written in the Book of Prophecies by the Master of Masters.