a box  

There are a few spots that take longer to spawn, otherwise - about 16 minutes. The spawn types are not set - you can get a barrel or a box, but the spots are the same. There are two spots on the third floor, that a melle type can kill - one close range, other ranged attack, that you do not have to worry about getting killed, other than that - there are mobs to close to the others and they will jump you when you attack.