I agree with Sov, this is truly an out of the blue RP, and the only reason, is because he killed one person. I'm sorry, but that's no reason for world domination. A good long story, and RPs leading up to this one are needed, if you want this to happen. RPs can't jut pop out of the blue, with no reason at all.
For example, if the Thieves randomly attacked the Enlightened, for no apparent reason other than they wanted to RP, it would be utterly pointless, there would have to be reason, a plot, a story behind it. Maybe they had openly shown resentment for us? And they had attepmted to destroy us before? Something along the lines of that would be good, in other words, try starting with some other RPs.
For example maybe the guild began killing certain people who were know for thier resentment of beggars and the poor [Aka XILLIX mwahahah jk jk

], and after a while, it began to get worse and worse, the RPs get bigger, the hate of this guild rising,several attempts at wiping them out failing, as they continue to slowly grow and form thier plan, until it is decided that they should be dealt with....but don't go copying this, think it up yourself, just go along the lines of gradual buildup. A good Rp takes time to form.
Soo....now my fingers hurt.