Thing is, there would be many, [i]many[/i] vigilante groups formed after the event. I would suggest saying the Black Knights are in fact a combination of most of these groups, rather than somehow trumping every other vigilante group. It could however be that it trumps or combines with most of the other groups in West Metropolis, but even then you would have to deal with other groups developing in West Metropolis itself.

Plus, if you character's the founder and leader, how would he interact freely with other characters? Your character's position in hierarchy would limit him to being in a building for his own safety, planning with others to make coordinated attacks on bandits and such. (Assuming it becomes all-mighty and powerful. If it doesn't, then it brings the issue of... joining other groups of characters with a whole bunch of vigilantes under your watch.)

Another problem I found is that your biography doesn't seem to acknowledge the destruction of the planetoid, instead just skipping ahead with transformation when your character decides to die in his favoured place. Like... there no real difference in time, between the planetoid being destroyed and the mist appearing, which was presumably next morning.

(I used the word 'presumably' because I don't remember the plot very well.)