This is for the main survival mode which has monsters, and whatever other mode it fits with. I will be working this out as I go.
So to give Rising World a history (the world, not the player). I suggest the temples, ruins, dungeons and other structures (surface or underground) are from ancient civilizations. Maybe NPC villages can be the descendants of these civilizations. 5 types of NPC villages for 5 types of ancient civilization which can be found (maybe 3 types of underground structures and 2 above ground? Whatever works...)? Just an example..
Each type of village could have an elder which tells of legends passed down through the ages about what the old civilization was like, type of structure they built and where it might be found (surface or underground, not specific information since the world is randomly generated), and maybe what kind of technology they used?
Yes, technology. As some of the best treasure to be found in dungeons and temples etc.., I suggest there is technology which the player can only get by finding these structures and surviving the monsters which inhabit them now. Each ancient civilization could have multiple technologies the player can use. But not all structures should have technology to be found.
Maybe you don't find the technology itself, but you find the blueprint (recipe). But I would prefer to find the actual technology and have to figure out how to recreate it. So reverse engineering.
Nothing crazy like uber computers or an android. Just simple, useful and unique tech. And you can't just know the crafting recipe for it and make it any time you want (no looking up the recipe online and within an hour of playing you've got ancient tech).
Maybe there is no way to craft these ancient technologies. You find the item, figure out how to use it and what it's for, and from there can only fix it by replacing parts. This way this tech would be pretty rare and it would continue to be valuable. You would have to explore and risk your life to get this stuff.. no getting your buddy to make several for you an hour after buying the game...
To give more for the players to craft. Finding these ancient structures could unlock new crafting recipes for other stuff. Simple things like chairs, new building materials like new window frames or doors, new lamps. Maybe even new things to grow in your farm by finding a seed packet. Find a sandstone temple and now can collect and build with sandstone. Also books and scrolls which could have stories of events, new food recipes etc.. All fitting with the lore of the civilization.
Lots of new content can be added through these structures, and with a bit of lore it will have some meaning in the world, it will be part of the world.. the world will be more then just the place that we mine, build and survive.
This can all be done at world generation.