A civilization that hasn't crumbled, or is about to start crumbling.
This is all that I want. A central hub kingdom with Tons of NPCs, civilians, etc. All dealing with the startings of the curse. You could be a high-ranking knight or officer at the start, a counsel to the king, who helps to cull the curse of the undead, until you yourself are given the curse, and exiled to the badlands outside of the kingdom. You try to tell your king that you aren't hollow, and that there are ways that society can move on and live with the curse, but he banishes you anyways.
When you are expelled to the badlands, you search through the remains of other crumbled kingdoms, looking for a way to stop or reverse the curse so that your king will accept you once more. You meet a small group of rebels at a base around a bonfire that become this games firelink/majula. Other former citizens, who have been exiled from the curse, and are planning revenge.
They send you on missions as they are mostly merchants or trainers, but they sometimes help you with bosses.
After a bit of searching, you find a way to reverse the curse, or at least to slow it, you seek to return to the kingdom, but find that the cure has spread and the entirety of the kingdom has fallen hollow. You fight your way through the streets to the castle where you need to find your king. It would get harder and harder as you approached the castle, moving from hallowed citizens to hollowed soldiers, then officers, then the kings guard and even demons which have seeped into the world.
You finally make it outside the throne room, and hear wailing from inside... you run to the door, your cure for the curse ready to present to the king.. but as you enter the fog door you see that he has become far too corrupt and hollowed to be saved. As it turns out, the curse has stemmed from his greed and scientific experimentation of which you were not aware.. The kingdoms only chance is for you to kill your former best friend and king, so that you can save everybody from the curse...