A Union (ユニオン, Yunion?) is a team of Keyblade wielders Player joins at the start of Kingdom Hearts χ. There are five, and each is led by a chosen apprentice of the Master of Masters called a foreteller: Anguis (アングイス, Anguisu?), led by Invi; Leopardus (レオパルドス, Reoparudosu?), led by Gula; Unicornis (ウニコルニス, Unikorunisu?), led by Ira; Ursus (ウルスス, Urususu?), led by Aced; and Vulpes (ウルペウス, Urupeusu?), led by Ava.
Each Union strives to protect the world from the Heartless and collect light in the form of Lux. The Unions compete with one another in a series of challenges, and in the aftermath of the Keyblade War, new individuals are selected to lead them: Ephemer, Skuld, Ventus, Brain, and Lauriam. Also chosen by the Master of Masters,[?] these Dandelions form a separate group known as the Union χ.[?] fending off the Heartless and collecting Lux. Assisting Union members on their journeys are a special type of Spirit Dream Eater called "Chirithy". When the Master of Masters disappears, his apprentices notice the Keyblade wielders under their wing are using Power Bangles that enable them to collect the guilt of the Heartless[?], but deem it acceptable for the time being.
After the possibility of a traitor existing amongst the foretellers is discovered, tensions begin to mount between the Unions. Foreteller Ava sees all-out war is inevitable, and she forms a separate group, the Dandelions, to escape to the world beyond and ensure light's survival. Per the Master of Masters' orders, Ava recruits five people to succeed her fellow apprentices as Union leaders.
With the institution of a Union χ, the Dandelions work together, regardless of the Unions to which they were originally loyal. They continue to protect the worlds after the Keyblade War, and they keep maintaining balance by gathering Lux.