[@NecroKnight] You certainly could make a knight who could defeat Robert. I mean, plenty of those existed, so long as you make it convincing or work up to that point. Also, I guarantee you will be able to affect change so long as you're not playing a stable boy, an unknown Knight's squire, or someone else who doesn't matter. Though, I will say. One man can certainly make changes. Look at Sir Duncan as one example or Rhaegar when he crowned Lyanna instead of Elia. (Admittedly Rhaegar is a little more prominent than Duncan.)