Union

The arcanocracy fostered by the Mage Sovereigns was built around Magic, and mostly arcane magic. While there were divine spellcasters among the Paragons and in service of the Lasarate, they were in an increasing minority compared to primal and arcane specialists.
Those Sovereignties ruled by a single immortal - the Holy Kingdom, Kavala and Porhola on the shining and frozen shores of Aino, and the city-states of the Heptarchy - Gods took rather a back seat to a twisted reverence of the self. This was not thought suitable for the masses, however, and so the Sovereigns created the Cults of Magic; a religious bureaucracy, responsible for deflecting worship to­wards earthly subjects, allowing the Sovereigns to reap the energies which would otherwise be - as they saw it - wasted on the gods.
Originally functional, over time the cults became what they seemed to be, a clergy. Some of the Heptarchs even co-opted the cults into their search for a divine spark to cement their immortality in the ascension to goodhood. The Sovereigns - even the most secular - began to be truly worshipped, to be seen as gods in their own right, as their power came to be represented by their churches.
The cults became indispensable, and in the manner of indispensible organisations, they became powerful: They knew more about the running of the Sovereignties, and the flow of power through the land, than even the Sovereigns themselves; save perhaps the God-Queen, who specialised in such magic. They became a buffer between the Sovereigns and their people, and as such were able to control the flow of information between them.
Early in their existence, the cults detected and suppressed scattered pockets of resistance against the Sovereigns. Later, they sought out and concealed, then fostered, more widespread and systemic discontent. This shift, by their own record, occurred after the cult tried to correct the sources of discontent, but learned that either they were things the sovereigns would not change, or that could not be changed while the sovereigns remained in power. Coming to believe that those they served were the ones at fault, the cults of different sovereigns began to talk, and to conspire.
The Union was a formal organisation arising from and embodying this conspiracy. Because of its origins, it very much maintained the form of a mystery cult, in the name of operational security. It provided a vital connection between the disparate rebel groups, and an essential sense of purpose and direction. It was the Union that allowed the rebellions against the Sovereigns to move with any kind of coordination. It was the Union who secured alliances with the artificers' guilds and the Bards' Colleges, which made it possible for the rebels to oppose the powerful members of the arcanocracy. It was the Union who cur­ated the Eightfold pantheon as patrons of The Uprising and the new order.
Throughout the War of Hubris, the Union was the central guiding and controlling authority of the revolution, but afterwards, it disbanded to allow power to vest in the civic governments and the Church of the Eightfold Way. Some, however, suspect that the Union persisted as a secret society, acting to control the Sacred Republic from the shadows.