Has 4 spawners, 4 chests, and 1 big chest, mobs are stronger and have a little more health, to unlock chests you need to kill mobs to get parts of a key, once you craft the key you can open a chest, each of the four chests contain a part of the key (and some loot) for the big chest, which contains the extremely good loot (like enchant books with the custom enchants?)
Has 4 spawners, 4 chests, and 1 big chest, mobs are stronger and have a little more health, to unlock chests you need to kill mobs to get parts of a key, once you craft the key you can open a chest, each of the four chests contain a part of the key (and some loot) for the big chest, which contains the extremely good loot (like enchant books with the custom enchants?)