Rebellion and Betrayal

Rebellion and Betrayal are options for the vassal of a more powerful House that seeks to become independent or align with another master.

Codex
"Because a vassal wields the military power of their territory, a leader's power is in great part based on their ability to retain the loyalty of their vassals. Vassals enjoy a great degree of freedom; as long as they do not oppose their master, they have every right to act politically and militarily to their own advantage.

A popular ruler or vassal leader may rebel against their master, hoping to gain enough support to become independent and withstand the inevitable military retaliation. A less powerful vassal on your border may instead choose to betray their allegiance to you, and give it to whatever power rules the adjacent territory. Both actions are dishonorable, but can be partially or wholly justified if the master has committed crimes against the vassal, or if the master does not have a legitimate claim to be the master of that vassal. Conspiring with someone else's vassal to receive their allegiance is also dishonorable.

When a ruler rebels, a new faction is formed that is immediately at war with it's former master, and the latter is considered to have a legitimate claim over the rebel faction. If the former master faction was a vassal of a league, the rebel faction is also considered a vassal of the league. An archon may tolerate squabbling between his vassals, but breaking away from the league would be a seperate crime against them."