The following is a description of the method I use in Creative Mode to take advantage of the Brown Mob’s ability to transmute one material into another. I am not saying that it is the only or the best method, but it has allowed me to accurately and consistently transmute one material into another:
I recommend assembling a Drill v3 before you attempt to capture a Brown Mob. It is possible to complete the following steps with your starter drill, but as you will see a faster drill is definitely better. Jetpack v3 is also helpful, it will allow you to jump all the way out of your hole.
Now it is time to find your Brown Mob(s). This step involves a little luck since there is no way to make them spawn, just walk around for a while. Often when they do spawn chances are that there will be more than one of them, be prepared to repeat steps 3 and 4 several times in order to catch as many as possible. Always mark your path with Mini Lights.
Walk up to the Brown Mob and place a block (any block) directly underneath it. What you are trying to do is to get the Brown Mob stuck inside the block you place.
Brown Mob Almost Caught in Block
Sometimes you will miss, just keep placing blocks until it is the center of the block.
Brown Mob Caught in Block
The next time the Brown Mob jumps you will see it go down into the block below it instead of up into the air. It will continue to go down each subsequent time it tries to jump, so don’t wait too long to start drilling your trap shaft or it will continue downwards until it reaches to lower limit of the moon where it will get stuck.*
Stand next to the block in which you captured the Brown Mob, drill that block and then straight down under it as far as you can from your current position. You should soon catch up to the Brown Mob and will be able to see it down the hole.
Brown Mob down Trap Shaft
The Brown Mob is now trapped and you can try to catch any others you may have seen. (Technically you don’t need to drill down more than 5 blocks, since the Brown Mob can only jump 4 blocks high, I just find it easier to keep track of depth if you drill as far as you can almost every time.) Mark the shaft and mark your path so you can find your trapped mob again.
Count 5 block away from the shaft and then 5 blocks to the side of the shaft (the direction doesn’t matter). In the photo, the Brown Mob’s trap shaft is in the center of the 4 mini lights (one is hidden under a red block) and there is 1 block between each red block. The red block with the light on it is where you will drill your entry shaft.
Location of Your Entry Shaft
Do not go into the same shaft as the Brown Mob.
Stand on the ground next to your entry shaft location and drill straight down as far as you can. Mark the inside of your shaft with a mini light to help you remember your orientation. The light should be behind you when you drop down your shaft (I usually stand so the Brown Mob’s shaft is in front of me to the right, but it doesn’t matter how you do it as long as you remember where its shaft is).
Drop down the shaft and place a mini light behind you. To one of your sides drill a 1 block deep by 2 blocks high landing. Step into the landing, and then continue drilling your shaft straight down as far as you can. Drop down the shaft again and place a mini light behind you. Drill down 4 more blocks.
Drill in front of you as far as you can, and then turn 90⁰ towards the Brown Mob’s shaft and drill as far as you can. You have now marked the extents of your excavation. In the photo I have drilled these marker tunnels all the way to the surface to show their position in relation to the Brown Mob’s shaft. Again, its shaft is in the center of the 4 mini lights and red blocks have been placed every other block along the tunnels' outside edges.
Brown Mob Trap Shaft & Excavation Extents
The excavation stage can be done however you prefer, but the goal is to excavate a 10x10x10 cube below the Brown Mob. Its trap shaft will be roughly centered above this empty cube. I usually stay in one spot, my entry shaft location, and drill everything out from there. In the photo there are mini lights on each block along 3 edges (except the corner, where you can only place 1 mini light).
Excavated Cube below Trapped Brown Mob
Choose the block you wish to transmute and place the blocks to fill your cube up with it. I will be using gold, since it will transmute into silver which you can’t find in Mooncraft version 1.7.0. I have found the most efficient way to fill the cube is to place a full height wall of blocks against the wall opposite you.
Full Height Gold Starter Wall
Return to your original location and start placing blocks directly in front of you. The first time you will place the bottom and second layer of blocks.
1st 2 Layers in 1st Row of Gold Fill
Then place a block beneath you, face forward again and place blocks in front of you. Place another block below you and repeat the process until you are 2 blocks from the the top. Then drop down to the side and repeat.
Once your cube is full, mine the next 3 layers of blocks above you. Move to the center, directly below the Brown Mob. There should be one layer of blocks above you, between you and it. Place a 5 block high wall of gold blocks around the perimeter of your square. Continue doing this until you are standing in a 6 block square. In the photo I have finished placing gold blocks and I've excavated everything above the gold cube except the 4 columns of blocks around the trapped Brown Mob. Excavating above the cube is not needed and was only done for illustration purposes.
Brown Mob Trapped above Gold Cube
Mine the blocks above you to let the Brown Mob in. Shoot it. It will then explode and you can collect your transmuted material.
Brown Mob in 6x6 Gold Room
Blocks of Silver from Brown Mob's Explosion
The reason for going through this complicated process is that a Brown Mob’s explosion can destroy blocks 6 blocks below it and up to 6 blocks to either side. In order to be sure the explosion is only transmuting the material that you want it to, you need the thickness. Silver blocks have been placed in the 2nd aftermath photo to show the product of the transmutation.
Aftermath of Brown Mob's Explosion
Aftermath of Brown Mob's Explosion Close Up
If anyone is interested I was planning to write another blog about how to do a similar thing in Explore Mode. It is far more difficult to use a Brown Mob's explosions effectively in Explore Mode.
'*'Along with a comment I wrote on the Blue Crystal page, about how to find blue crystal by forcing the transparency bug, I also wrote a warning about the possibility of getting stuck while using the method I described. It turns out it isn’t saving the game, while your head is in the block above you, that causes you to get stuck. You’ll get stuck if you jump after you’ve placed the first block below you and then place another block below you. In my opinion, this will make it so you are stuck in the center of a block, just like you’ve done to the Brown Mob. If you immediately drill your way out of the situation you won’t get stuck. If instead you continue jumping, forcing yourself into the next block down, you’ll eventually reach the lower boundary of your moon. If this happens you will be stuck there forever.
