Alright a few things to discuss here. 1: the chests are in the "lobby". 2: try not to stand by the walls as creeper explosions will destroy it causing mass amounts of slimes to come in. 3: the spiders dont fit through the hole so feel free to change those spawners. 4: you will be fighting the following- skeletons, zombies, creepers, blazes, pig zombies, (and whatever you change the spider spawner to). 5: i made this in regular creative mode and i didnt plan it pout very well but it pretty much looks like a colloseum. thats it basicly. try to survive the onslought and have fun!