My Brother's Keeper

My Brother's Keeper is a hidden trophy/achievement in the Zombies mode map Der Eisendrache that appears in Call of Duty: Black Ops III. It is the main easter egg of the map,  and it requires the player to erase the original "Tank" Dempsey. This also requires to continue on with Richthofen's plan, purging Group 935 and Groph (at Griffin Station) as well as blowing up the Moon. This relates to the fact that in the Moon Easter Egg it requires the player to blow up the Earth and switch bodies with Samantha.

Step 1: Obtain the Ancient Bows
Obtain and upgrade the Wrath of the Ancients to any of the Ancient Bows. For a detailed guide to obtaining and upgrading the bows, please visit their respective pages.

Step 2: Charge the Teleporter
Go behind the tomb and obtain an original Wrath of the Ancients. Individually shoot each antennae/prong on the top of the teleporter in the undercroft until all of them have a yellow tint. The player will hear an audio cue when done correctly.

Step 3: Shooting the Sparks
Around the map there will be random objects that could possibly be sparking. Only one object will be sparking at one time and the player will hear a cue before it starts to spark. Shoot the sparking object with any upgraded ancient bow and it will stop sparking. Shooting with anything else will result in an instant failure. The player will hear another cue and have to repeat this process three more times. After four sparking objects have been shot, the player will hear a different cue indicating they have completed this step. If the player takes too long or messes up, they will hear a failure cue which resets progress on the step and is unable to be resumed until the next round.

Step 4: Time Travel
Return to the teleporter and the bottom light will have turned purple. All players in the game must be in the teleporter in order to teleport. Once the player teleports, they will now be in the same room but it will be cleaned up and obviously in the past. Here, the player cannot shoot, aim down sight, throw grenades, use the Ragnarok DG-4 or do anything. Dr. Groph will be here talking to Richtofen over radio and accessing his safe. Here the player must do three things before they are teleported back:

Hold the use button to pick up the blue canister in the corner of the room near Dr. Groph. Hold the use button to pick up the briefcase located to the left of the door. Remember the three symbols from top to bottom on the door of the safe. If the player does not achieve all three goals above, they are able to repeat steps three and four every round. Note, however, that the symbols will change with each teleport.

Step 5: Death Ray and Cracking the Code
Interact with the death ray on the side facing the clocktower to add a fuse to the side, then go to the other side and pull the lever to switch the Death Ray from "Destroy" to "Protect", then turn it on. Afterwards, head to the terminals near the clocktower and enter the three safe symbols in order top-to-bottom. This will open the safe across from the teleporter (the same safe seen in the past).

Step 6: Memory Simon Says
Head to the safe and interact with it to pick up the two fuses and the keycard. Insert each fuse into the Tesla Coils on either side of the Death Ray, then return the Death Ray to "Destroy" mode and turn it on once more. Head to the terminals outside of the clocktower and interact with them. This activates a memory game of Simon Says. The four symbols on the bottom screen will show for a couple of seconds before disappearing. Memorize the symbol's locations. The top screen will then show a symbol and the player must interact with the screen correlated to that symbol. Do this a number of times until the machine shuts down and the player hears an audio cue. Repeat the game of Memory Simon Says at the terminals at the rocket launch site. If the player fails the game they can instantly restart the game by interacting with it again.

Step 7: Sabotage
The orbs atop the Tesla Coils will now be glowing. Interact with the green button on the back of the death ray to initiate the rocket crash. A rocket will appear in the sky and fly across until striking the bell tower (destroying the bell) and landing in the courtyard below. Dr. Groph will express his anger and lock down the cryogenically frozen Tank" Dempsey, prohibiting the player from interacting with it.

Step 8: Purification and Return of the MPD
Look around the crash site, find the Vril Generator sitting in the snow, and pick it up. Place it in the slot on the side of the tomb (in front of the location where the player obtained the Wrath of the Ancients) and a ghost keeper will rise out of the tomb. He will start traveling the map and stop at four separate locations. A white circle will appear on the ground. If he stops by Double Tap Root Beer 2.0, interact with the part of the wall to the right of the keeper and under the lamp post to place a stone tablet. This must be done. When inside the circle there will be a colored tint around the screen. The color of the tint correlates to the bow the player must get kills with while in the circle (e.g. an orange tint = get kills with the Fire Bow). The stone tablet by the circle will fill, and once full the ghost will move to the next location and repeat the process. After done four times, the keeper will become solid and travel to the undercroft. The pyramid will transform into a similar MPD from Moon and then open. The keeper will hover inside the space and stay there. All players must take their Ragnarok DG-4 and use the trap function on each side of the square on the ground. They will then be teleported away.

Step 9: Mysterious Keeper Battle
Here the player will meet the Mysterious Keeper, the boss of this area. He has four attacks that mirror all four Ancient Bow abilities. The attacks are as follows: a rain of skulls that come down in an effort to slow down the player, spawning either skeletons, which act like zombies but with the model from Dead Ops Arcade 2: Cyber's Avengening, or Panzer Soldats, volcanoes like the ones created when the fire bow is fully charged and hits an enemy which, when touched, deal enough damage to down a player without Juggernog, and electric shockwaves similar to the Death Ray. To avoid the electric shockwaves, one must take cover behind one of the pillars in the area. Within the few seconds before the electric shockwaves commence, however, there is an opportunity to damage the Gatekeeper boss. Plant the Ragnarok DG-4 in the electric ball in the center of the arena, and the Keeper, after the shock, will be planted in place. A purple rend will appear on his chest; fire the upgraded bows in here in order to damage the boss. Note that this will take at least eight attacks to defeat the boss.

A Max Ammo will drop after each time all of the Panzers are defeated, so ammo is of only minor concern. It is possible, however, to run ammo supplies dry during the first portion of the battle. It is therefore recommended to bring weapons with high mobility and high ammo count, such as the Pack-a-Punched Man-O-War or Haymaker 12, or a light machine gun.

Step 10: Sky Destruction
After defeating the Mysterious Keeper, the player will be teleported back to the MPD. Here Dr. Groph will express his extreme anger at the group and vows to destroy them. Pick up the Summoning Key from the side of the MPD. Richtofen will explain that the player needs to charge the key in order to retrieve the test subject. Take the key to the terminal next to the now bell-less bell tower and interact with the terminal. The key will hover above the terminal and the launch will be initiated. Multiple rockets will be blasted at the moon, ultimately shattering it. A cutscene will play. Afterwards players are returned to the deceased test subject, given all perks on the map, and a brief immunity to any damage.

Trivia

 * Ironically, the original timeline Dempsey was killed by his own younger self similar to how the original timeline Richtofen was killed by his Origins self.