I know it would be unrealistic, but being able to reatatch limbs to make a weird humonculous would be cool. It would fit with the horror aesthetic, doing horrific things to a person in a dungeon.
This game reminds me of the dr mods from wxsand, where you could kill and revive someone over and over, doing weird things to them, like giving them illnesses or zombifying them. Except you can't revive him in this, other than resetting to the beginning. That would be nice.
If you ever want to add something that is magic/scifi, you could keep it in the aesthetic by making it eldritch magic I guess.