The Cavern is a 1.12 puzzle/adventure map about collecting and exploring a large cavern filled with traps, enemies, and security. It was inspired by this Mumbo Jumbo video:
Most of the adventure map takes place inside normally spawning cave systems that have been souped up with puzzles, monster spawners, etcetera. The map can be played in singleplayer and multiplayer, with as many players as you want. There is no goal, besides get to the end, and there isn't much story. Let's plays on YT are allowed, and in fact, highly encouraged.