You might not know it, but inside this 32 block high structure, there is a grinder that sorts between Zombies, Skeletons, and Creepers. And it's all done in vanilla minecraft, with NO command block trickery. It is an easy way to get lots of drops from these mobs. (and sometimes Spiders and Witches as well... Nothing I can do about them)

Here's how it works:

You're probably wondering, how am I sorting out Zombies, Skeletons, and Creepers with this grinder? Well, allow me to explain:


At the top of the structure, there is an area for mobs to spawn exactly 100 blocks from the ground. (this is essential for allowing lots of mobs to spawn unless you have torched out all caves within a 100 block radius of where you'll be building) There's nothing special about this. The mobs will spawn, be stupid and fall in the water, and make their way down to the sorting area.


In the Sorting Area, there are three chambers for the mobs to fall in. (one for each mob) The only problem is that the mobs' AI is random and there's no way of knowing where they'll walk, if they'll walk at all. Fortunately, there's a way to influence this. But we need the help from a few special friends.

Zombie sorting:

Zombie sorting is incredibly easy. There is a Villager just out of reach in a fenced area that the Zombies will be attracted to. There are trapdoors that make it impossible for the Zombie to reach the Villager, thus they will fall down a 21 block shaft to their respective grinding area.

Skeleton sorting:

Skeleton sorting is a little more difficult because there is nothing that Skeletons are attracted to. However, there is something that they are afraid of... In the sorting area are two tamed Wolves, one in the wall of the Zombie shaft and one in the wall of the Creeper shaft to help prevent the Skeleton from going in those shafts and help go in his own. They need to be tamed and sat down or else they will go after the Skeleton thus killing it and/or falling down one of the grinding shafts.

Creeper Sorting:

Creeper sorting is possibly the hardest one to do. It is exactly the same as Skeleton sorting, however it's with Ocelots. In addition to Jungles sometimes being hard to find, Ocelots are kind of hard to tame. Once you have two, though, you can finish the Creeper sorting by putting the Ocelots in a hole in the wall. (one in the wall of the Zombie shaft, one in the wall of the Skeleton shaft)


After the Sorting Area, there is the Grinding Area. The three mobs are sorted and fall in their respective shafts with 1 heart of health, making it easy to kill them with a single swipe of a sword and gain their drops and experience. (sometimes in addition to Witches and Spiders, again I have no control over them) The shafts are also designed in such a way so that the mobs, especially the Creeper, will not try to attack you. This is extremely useful if you are going in an afk session. Speaking of being afk, there is a special lever besides each shaft that converts it from EXP Mode to KILL Mode. Any mob that drops in their shafts, (sometimes excluding Spiders and Witches) will be killed instantly and the drops will be siphoned into their chests.


*Notes:

• While in Kill Mode, mobs will not drop their experience.
  
• There will be occasions where some mobs will sometimes be dropped into the wrong shaft. This isn't a big deal, but it is kind of annoying.
  
• This farm is Enderman proof as the area for mobs to spawn is two blocks tall. Mobs (other than guardians and squids) also cannot spawn in areas where there is a fluid block. If there were no water in the spawning room, this would provide the three blocks of space an Enderman needs to spawn.
  
• Occasionally, the mobs can be pushed back to the point where you cannot hit them. If this happens, flick the lever to their respective shaft twice and it will suffocate them.
  
• You must be in/near the Grinding Area to receive drops from the farm. Otherwise, mobs will not spawn.
  
• This farm will take a while for you to build and will require a LOT of building blocks.
  

There is a world download which you can use to try out the farm and get a good look at it. I hope you like it, and I'll see you in another post.