The castle in the clouds is where the upper class lives and no one from the middle or lower class has ever been inside until Rsiran.
Brusus and Rsiran where in a warehouse full of “goods” when police showed up and forced him and Brusus to fight off the police. during the fight Brusus had been stabbed. Josun does business with Brusus but is shady and goes behind his back and threatens to throw him and Rsiran under the bus if he doesn’t give all of the elaeavith a poison that will “temporarily” disable their abilities. Rsiran does this but instead of it disabling them it kills all of the elaeavith and Josun plans to blame Rsiran for all the murders and reveal Brusus, but Rsiran slides his knifes covered in poison and kills Josun while in the castle.
After Brusus is awake and he is a the tavern with all his lower town friends. Rsiran thinks about what his father said he would become and he was right. But doing all those things saved his friends in the end, and he can live with that. He comes to realize that maybe his dark ability, isn’t so dark after all.