Caves should have one mob

Mobs would be 'terrorial' underground. You walk into a cave, you don't know who might live there. Maybe you see a clue first - a web, then you can expect spiders, a lot of moist moss you can expect zombies, bones laying around you watch out for skeletons, perhaps a plentiful mineral attracts Endermen or some other mob. As an added puzzle, there might be objects in each mob's realm that together might piece together and form an amulet or armor of protection against that mob. For example, steal a witches hat and combine it will beetroot, and witches can't harm you. At the end of each cave has its own boss battle, with a big version of the regular mob. Perhaps the prize could be some weapon or armour related to that mob 'culture'.