Lust for life
The Rebellion is a movement initially started by a group of people in the Jhereg controlled part of downtown. They refused the oppression of the higher born and demanded a new government. They were preparing to take it by force but then the first Blight happened.
In one of the sessions the leader of the rebellion was murdered by the party as requested by Vlad. Cawti took over his roll however, much to the dislike of Vlad.
When the Blight appeared, the goal of the Rebellion shifted.