The Guild
The Guild is the super power in the series and is ran by Maestro Delphine. They live high in the clouds and are the strongest faction in the world of Prester. They give the claudia units to the Disith and Anatoray that allowed the two factions to wage war and also control the set of rules that govern warfare. It is unknown how the Guild received all this power when the colonists came from Earth (because the Guild has it and Anatoray/Disith don’t), but we know Exile is what gave it to them.

When we break down the Guild we can see it is a dictatorship ran by the Maestro. Everyone in the Guild is basically a mindless zombie that follows her commands. Delphine and Dio seemed to be the only ones with any free will.

Right of the Covenant and Trial of Agoon
The Right of the Covenant is a test where nobles in the guild fight to the death for the Sword of the Covenant. Whoever manages to get the sword will inherit the title of Maestro. The Right of the Covenant happens when boys in the guild turn 17. The actual fight is called the Trial of Agoon.

The Right of the Covenant is what Dio feared so much because once has was captured by Delphine, he was changed by some machine and lost his personality and free will.

The Rebellion
Throughout the show we see former members of the guild (Ressius, Marius) and hear them mention a rebellion that happened in the Guild. From what I have gathered, there use to be four houses that made up the Guild. Dagobear, Eraclea, Hamilton, and Bassianus. I’m thinking House Eraclea (led by Delphine) tried to take over everything in the guild, and in the process ousted the other three houses. We know that Marius of House Bassianus had escaped the guild aboard a warship. We’re not sure of how Ressius came to the Silvana but that he was of House Dagobear. And lastly the House Hamilton escaped to Anatoray because they gave Alvis, or the “cargo”, to the Silvana.

When (once again this is a theory because it isn’t touched on very much) Delphine got all the power, she must’ve changed everyone in the Guild to be mindless zombies like they currently are. I don’t think they use to be like this because members of the ousted houses have minds of their own.