i gotta admit its a lot of very hard to do answers. my thoughts would be that a game like this would use a system similar to that of those open-world LOTR game where you have a whole hierarchy of asshats that fight over each other and occasionally you or civilization. That or maybe something from another roguelike: Dungeonmans. In that game if you die in a dungeon, the guy who killed you gets a fancy name and title and becomes the new guy running the dungeon. If you died in the overworld or something then a new looter camp or dungeon would pop up with your killer chillin there along with the bones of your previous dungeonman.
Yeah that system is pretty cool, but the way our game is right now, hero deaths are not really guaranteed to happen, and might be just too rare to count on, depending on the difficulty level. We also don't have a persistent world in the same way, the lands are generated fresh each time. But so yeah those are great ideas, but there's also some distance between "here is a bandit" and "here is an epic 100-year storyline", and that's the thing we're really trying to solve here. Legacy monsters sound awesome though and I'd love to revisit them.