Ushevan Only guys with a actual ideological motive for rebellion rather than as a matter of survival or just being oppressed a bit too hard
(Except for Operth V I guess but those guys just seem like a buncha psychos)
+1 to Ushevan. Having an actual ideology will make it much easier to spread the rebellion. All the other planets' casus belli seem pretty particular to themselves.
Ushevan
The rebellion began in
Ushevan to great fanfare among the hard-bitten frontiersmen whose fathers and grandfathers first set foot on their desolate world. Generations ago, they considered the planet to be a fresh start for the Imperium and today, the gathered Secessionist leadership could not agree more. You are the foremost of the assembled men and women here, it was your tongue that gathered the fuel of doubt, your vision that lit the fires of rebellion, and your cunning that kept that flame from being extinguished in its infancy. The others fought or schemed, where you spoke, and in the end, it was your voice that cast the Planetary Governor from his petty throne. You've earned the absolute respect of your inner circle and many of them consider you the father of their rebellion, but you know that the struggle for independence has only just begun.
What is your name? (You can describe the Common Demagogue's appearance and mannerisms as well, if you'd like. He'll be your viewpoint character for the rest of his lifespan, outside of exceptional circumstances or a change in the rebellion's leadership.)
You lean back in your chair, close your eyes, and think of how you came to be here. You think of years spent tilling hard soil for meager returns, years of thinking without care for doctrine, and years of carefully planning how you were going to seize control. The war was decided before the first lasbolt was shot. Even if the Forge World Euclite hadn't sent word from the outer system of their support and put meltaguns and krak grenades in your men's eager hands, you would have rebelled. They only guaranteed your victory, and you are forever grateful for that. The Fabricator-Locum Iotapianus Falasco was sent to represent his planet on the Fabricator-General's behalf and has a place of honour here. All of the Euclite Mechanicus do. You believe you could have made the first step without them, but making strides through the Sector would have been impossible. With their industrial support, now anything is possible. You think of the driving force behind the Ushevan philosophy. Its start was rocky and slow but when the rumours caught on despite the overseers' best efforts, they spread with incredible speed.
At its core was a single, groundbreaking idea that went against everything the Imperium stands for. (You can suggest another if you like, as long as it contradicts the Imperium's fundamental worldview. This is the initial core tenet of what will likely become a more complicated ideology if the rebellion survives long enough.)
Meritocracy: The idea that only those with clear, demonstrated skill should hold power. Fairness: The idea that institutions should be unbiased and accountable for their actions.Equality: The idea that none are inherently inferior or superior, no matter their status.Freedom: The idea that the people should act as they will, without higher restriction.Atheism: The idea that no higher power has the right to dictate how the people live.Pacifism: The idea that war is not glorious and should only be fought to bring peace.