Part of my thoughts could be put to use as a story or just a dungeon run. Even a DM/GM can use it as an idea for a story on game night around the table.
The idea stems from ghosts and character deaths but deep inspiration comes from the Shadows that you can encounter in the Shroud of Souls, with the updated animation of dying status in which you character now lays on the ground dead brought forth the extended thoughts of ideas. When a Shadow kills your character and they die from no help getting them up, there should be a dungeon or story in which your hero returns as a ghost and must get help in order to be revived before any soul harvesters or enslavers come to the area where your hero died, leading to an interesting story a bard can eventually retell.
The dungeon idea is that it'll be a dungeon of 10 players, 5 alive and the other 5 are dead and are ghosts trapped in special soul containers that the living heroes must find and set free. If all 5 dead heroes are saved, all players get a good bonus at the end of the dungeon. The dead heroes are bonded to the living heroes, the living players must decide who will get which dead hero and are 'bonded' with the dead hero in which they get a boost to their stats depending on the dead hero's, can be randomly selected. Once bonded to the living hero, the dead hero is able to use their abilities for a limited amount as they will be draining the hero they are bonded to of their stamina which will lead to tough decisions in which should the dead hero use their ability to help or let their living hero use their stamina when they need it.
In example, a dead cleric will want to use a healing spell and will drain the barbarian's stamina when they would need it to block or run away from a threat. A warlock can inflict curses using a fighter's stamina in which also boosts the fighter's attack on said cursed enemy.