You can make the game be the story of one family or organization's attempt to kill the final boss. The character the player is controlling is then just one part of that overall attempt; each individual will then in some way get the organization closer to their ultimate goal -- and your score will reflect how many bodies you accumulated along the way. The best score, but also the most difficult game, comes from winning the entire thing with only one character, but that might be impossible or at least incredibly difficult. Once the boss is defeated, the organization (i.e. savefile) is retired.
Compare with Spelunky, which is a sort of roguelike/platformer game. The game is broken up into 4 sets of 5 levels (cave/jungle/ice/temple), and when you make it to a transition between the level sets, you're given the option to trade away treasure (i.e. points) for progress towards digging a tunnel (i.e. shortcut) to the next region. The shortcuts get your later characters closer to the endgame, thus making it easier to win -- but you sacrifice points by doing so, because you aren't playing some of the levels and thus miss out on treasure. The best scores come from games that play every level in one sitting.
So I think this gels nicely with your ideas on having multiple lives, different regions in the dungeon, and so on. The question really is how you go about adjusting the difficulty of each "life" based on the exploits of the previous characters. Should the game ultimately be winnable by anyone willing to simply pile up a large enough body count?
Compare with Spelunky, which is a sort of roguelike/platformer game. The game is broken up into 4 sets of 5 levels (cave/jungle/ice/temple), and when you make it to a transition between the level sets, you're given the option to trade away treasure (i.e. points) for progress towards digging a tunnel (i.e. shortcut) to the next region. The shortcuts get your later characters closer to the endgame, thus making it easier to win -- but you sacrifice points by doing so, because you aren't playing some of the levels and thus miss out on treasure. The best scores come from games that play every level in one sitting.
So I think this gels nicely with your ideas on having multiple lives, different regions in the dungeon, and so on. The question really is how you go about adjusting the difficulty of each "life" based on the exploits of the previous characters. Should the game ultimately be winnable by anyone willing to simply pile up a large enough body count?
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