This is the main easter egg for Der Eisendrache, it seems like a real doozy, but the only really difficult part to this is the final boss fight at the end.
It can be done with any number of people, however, I recommend you do not do it with 3. This may have been patched, but with three it is much more difficult then with any other number of people based on how many bows you are required to build. The only step requiring more then a single upgraded bow built is the keeper escorting step. I'll explain this more in detail later, but I can confirm that with 2 people in the game you only need 2 bows built, one per person, with 1 person in the game you need 1 bow built, and with 4 people each person needs to have built a bow. However, with three people you would think you only need 3 bows but from experience all 4 need to be built, if someone can confirm this otherwise please let me know, it may have just been on my end, regardless this is easiest done with 4 people anyway. Edit: the way to do this with three, or any number less than 4, is to make sure you are in a ranked game, this means people can not join the game in progress. If the game is unranked, the game prevents you from doing all steps up to the boss battle with few players so fewer bows can be built, and then having more join in progress to make it easier. So basically if you have 4, make sure the game is unbanked so if someone disconnects they can join back in. But if you have fewer make sure it is on ranked so you only have to build as many bows as there are players. I recommend 3 people as well, as you would not need to do the fire bow, which can be very expensive and time consuming.
Pre game
There are no gobblegums required for this easter egg, but certain ones make it easier, especially during the boss fight. Phoenix up is helpful if a player downs so they are instantly picked up and keep all their perks, although its rare, klling time is also helpful in the fight. Besides that it is really personal preference, I like In plain sight, but its up to you.
Step 1: Building bows
The first step is to build the wrath of the ancients and upgrade it, one for each player. The difficulty in upgrading each bow varies, in order from easiest to hardest in my opinion is: 1. Lightning bow 2. Wolf bow 3. void bow 4. fire bow
So if you're doing this solo only upgrade the lightning bow, with 2 people have one person do lightning, the other wolf, for 3 and 4 you will need to do all 4 bows. With 3 people, one person will need to finish one bow and start on a second. I recommend the host do the fire bow, as it makes the mid air shots much easier.
I'm not going to go over each bow here, I made a guide for der meistrobogenshuetze (I know it's spelt wrong, sue me) just refer to that or any other guide.
Step 2: Wisps part 1
This step requires at least one person have upgraded their bow. It is however best done with 2 or 3 people.
To begin this step, a person carrying a non- upgraded bow (wrath of the ancients) must head into the teleporter room and shoot their bow at all 6 glowing blue orbs on top of the teleporter. You will know this done right when you hear a loud screeching sound (this is supposed to be a margwa, don't worry there's none on this map) As soon as this happens a timer begins. Your task is to seek out 1 of 8 possible objects aroud the map, one of which wil be glowing with electricity, the locations of the 8 objects are:
1. The clock above the fireplace in the church
2.The radio in the chruch, on top of some computers to the right when looking at the clock.
3. In the power room, adjacent from the door leading to the death ray there is a phone hung on the wall.
4. In samantha's room there is a globe.
5. A car tower near double tap
6. Right beside quick revive there is a phone
7. In the barracks there is a clock on the wall, top floor
8. By the work bench above double tap, there is a box
If you find a glowing object it must be shot with an upgraded bow, after a few seconds another margwa will sound, signalling a new one has spawned, four in total must be shot, changing every attempt. I suggest you have 2 people looking for 4 objects each, each with an upgraded bow. Something of note, it seems that if you accidentally shoot your bow close to an object that isn't glowing it can fail the step, signalled by a noticable soud. If you are unable to get an object in time and fail, it will automatically begin the sequence again when a new round starts.
Step 3: Back in time
When the wisps are completed the teleporter will turn purple, all players must stand on it before activating, and it will send you back in time. You will see a doctor putting items ina safe, you need to worry about 3 things while this is going on. The first is picking up a blue container on the left side of the room, the second is picking up a fuse on the right side of the room, and the third is paying close attenion to the safe as the doctor shuts it, he imputs a 3 symbol code, which you will need to remeber. It will automatically teleport you out of the room and in to the rocket test area.
A panzer soldat will spawn so get rid of him quick, ensuring you dont kill the zombie, so lay off the bows as there's a good chance you accidentally kill the remianing zombies of the round with. If the round does end you will need to re- do all the way back to the wisp step so be careful!
Step 4: Imput the code
Now you must head to the death laser area and walk up to the activation.
Hold 
on both sides of it, on one side you put a fuse in and on the other you switch the dial to protect mode. Doing this spawns an infinite round of dogs, which continue to spawn until the next step is completed. Head down the stairs to towards the clock tower and you will see a series of computer screens, go up to it and hold . This will cause 4 symbols to appear on the 4 screens, you simply must input the code you saw on the vault earlier by holding on the right screens.
Step 5: Samantha says (kind of)
Now you must head to the teleporter room and look for the safe that the doctor closed earlier. Hold on it to grab the pieces inside.
Now head back up to the death ray and look at the two pillars on either side of the area. Each one is missing a small electric piece, which you just grabbed from the safe. Hold on each one to place it in, and then make sure the death ray is set to destroy not protect, also make sure the death ray has been activated at least once.
Now you need to play a game using the computers you inputted the code on. Go up to these computers and hold , the four smallest screens will show a symbol briefly, you need to remember the order of the symbols. Additionally, infinite dogs spawn so have someone protecting you while you do this. The big screen will show a symbol and you need to hold on the screen that just had the same symbol on it. Do this about 5 or 6 times and you are done, its pretty easy. Now you must head down to the rocket test area and you will see similar computers right by where the PaP spawns, do the same thing here.
Step 6: Tank 1.0
You will know if you were sucessfull with the previous step if both the electirc spire things you placed the pieces in at the death ray are glowing at the top. Now hold on the green button at the back of the death ray. This causes a rocket to crash down in the upper courtyard, carrying with it a Tank Dempsey from another timeline (I'm also confused).
By the wreckage there will be a golden rod, if you did the Call of the dead or moon easter eggs in black ops 1 you will recognise this thing, grab it.
Step 7: Wisps 2
Simple, do the exact same thing you did for the first wisp step, the locations of the wisps will have changed though.
Have all players be on the teleporter and activate it, heading back to the past.
Once you are here, you must activate a switch to the right of the room, which opens a box across from the teleporter, which contains a stone tablet you must grab, you are automatically teleported out.
Step 8: Escorting the keeper
This next step requires all players have built their bows. Make your way to the area where the wrath of the ancients spawns, there is a tomb here with a spot for the golden rod. Hold on this spot and a ghost type thing appears. Start folowing it. It will eventually stop and form a small glowing ring in front of it. The more people standing in the ring the bigger it gets. While standing in the ring, the sides of your screen will glow a specific colour. This indicates the necessary bow you must get kills with. Orange for fire, blue for lightning, green for wolf, and pruple for void. Whoever is carrying the necessary bow must get kills with it while standing in the circle. It is easiest if all players are here, and that only the person with the correct bow get kills, unless you begin to get overwhelemed. You will see the souls from kiled zombies go into the wither.
Once enough zombies are killed the keeper will begin moving again travelling to a different circle requiring a different bow. Repeat this until you have done for circles.
When the ghost reaches the area near double tap you must place the stone tablet you got from the box on the wall befoee you can get kills.
Once four are completed the witch will head down to the pyrmid room, playing a bit of a cutscene (all zombies temporairly despawn). When this is finished the pyrmaid from moon will appear in the center of the room. One of the four blue soul containers is missing, luckily you grabbed this earlier. Place it and get ready for the boss fight!
Step 9: Fighting the keeper
Now time for the only real challenge of this easter egg. Fighting the keeper. To start, all players in the game must place their ragnarok's down (with 
after equipping them with 
and 
) on one of the four panels that activate low gravity mod. Before you go it is very important you prepare like crazy.
Go as many rounds as you need to make sure everyone has 4 perks. You will aslo want at the very least 2 people (if playing with 4) with either a brecci or a haymaker pac- a- punched, these are by far the most effective weapons for dealing with panzer soldats. Which there are alot of. The most effective weapon for killing the boss is the upgraded Drakon sniper, so try to have at least one person with that. As well as monkey bombs, these are very important. When everyone is prepared enter the arena.
You may want to up your brightness because it is very dark in the arena. There arw three threats while you're in here:
1. Zombies (look like skeletons)
2. Panzers
3.The keeper
The keeper has a number of attacks, I dont find the keeper to be that much of an issue, the panzers are more dangerous. The way to attack the keeper is by waiting for it to do this electric attack, which causes a ball of electricty to spawn in the very center of the room. When this happens quickly run up to this electricty and have one player place the ragnaroks down. This will temporarily open up his chest for attack, which is glowing yellow. Unload all you got into the chest during this time, spam the crap out of your bows and throwing a monkey is a good idea so the zombies don't bother you. If you are unable to place your ragnaroks down you need to hide behind one of the four pillars around the room during the electric attack, because if you are anywhere else the electricty will insantly down you. This is only a real problem doing it solo because the raganarok needs to recharge, but with 4 people there's usually always a player with them ready to go.
There are 3 stages to this boss. The first stage is easy because there are no panzers, and you should be able to take down all his health for the stage with one use of the ragnarok.
Once the first stage is done, a max ammo will spawn in the center of the room, the keeper will dissapear and you will be faced with the second wave, just panzers.
These panzers are much stronger then the one's you would see normally. They have a massive amount more health. Typically a pazner can be killed by about 1 magazine from an upgraded haymaker, but these ones take 4- 5 magazines. As well, before shooting them with any upgraded bow would temporarily freeze them, but this is no longer the case. Keep moving and shooting there are quite a few panzers here. Monkey bombs wont really help you since panzers don't atrract to them. Spam the crap out of your bows as well.
When the last panzer is killed the third wave begins, which is the keeper and panzers at the same time. Nothing really new here, keep an eye out for the electrcity in the center of the room for the ragnaroks, and dont shoot the keeper unless there are no panzers nearby.
This wave he has considerably more health then the first wave, and will take you multiple rounds to take him out.
After a while you will eventually finish him off and be teleported back.
This fight is quite difficult and requires all players really know what they're doing. The tric is to keep moving in the same circular direction and keep laying down fire with your bows.
Final step: blow up ze moon!
When you get back hold twice on the circular formation on the pyramid.
Now head up to the computers by the death ray and hold , this will launch a number of rockets towards the moon, blowing it up (sound familiar?). And hey, you're done! An interesting cutscene will play and you'll get the achievement and all perks.
*It may have been patched by now, but please note that many people have reported being actually killed during the final cutscene, ending the game before they get the achievement. This is likely because the cutscene is entirely rendered in engine not just a movie,(its kind of hard to explain but just trust me on this). As such they are suseptible to damage as normal, the best remedy for this is to make sure you don't press the computers until you have only one zombie left in the round. And have one character take him as far as possible from the area teh cutscene takes place (the upper courtyard just outside the church) it is unlikely this glitch even occurs, because the zombies are supposed to all despawn, but its a necessary precaution unless you want to risk needing to start from scratch.
Anway, hope this helps, this easter egg is actually pretty easy, certainly much easier then the full Shdaows of Evil easter egg. The boss fight can be a bit of a challenge but its doable.
Good luck!
