What do you guys think yay or nay I mean i already have a past save with me, so to destroy or to not destroy the whole chapter. Can anyone list me the pros and cons of what will happen when I beat this quest?

Those are spoilers man. My good characters always destroy them when it becomes personal. Even then, ever since I've done the ending of the DB, I can never do it again.

No pros really, you just get rid of some assassins. Not much gold for it, but you can get their clothing and the unique clothing from Nazir.

Aside from being able to fill the Ebony Blade with a few souls (why it works without doing any quests for them I don't know, but I'm not complaining), the only real reward is that feeling that you prevented a great deal of death and tragedy. You also miss out on things like

But the DLC's and the other guild quest lines will make up for those.

Spoiler edited sorry i overlooked it.