This can be very difficult because of the challenge to fill 4 chests. I highly suggest setting it to Easy difficulty.
In the spawn, up the stairs to the left is a 'Ritual of the Ancients' board that has challenges for you to complete (another out by Generator Station 6). If you aim at each medal it will bring up a challenge. The challenges listed are:
1. 115 Normal Zombie Headshots - Rewards Lamentation / Afterburner / Spatz-447 / Agarthan Reaper
2. Capture 6 Generators - Rewards Max Ammo
3. Spend 30,000 points - Rewards Double Tap
4. Fill 4 chests to capacity - Rewards Thunder Fists
Challenges 1-3 are individual. Challenge 4 counts for all players. Thanks to ClockWrkPhantom for confirming this.
Every time you complete a challenge, a medal will appear above your perks. You can then head to the stone chest where the challenges are listed to gain a reward.Headshots and Point Spending
This is pretty straightforward. If you open up the entire map/buy perks/hit the weapon box/etc. You'll spend 30 grand in no time. SMGs or Assault Rifles are excellent for headshots. The STG-44 in the Church has the highest headshot damage multiplier for a weapon you can buy off the wall, so I highly recommend it.Generators
For the six generators and how to capture them, refer to my solution on 'All Your Base'. As stated above for this challenge you do not have to have all six captured at one time, though you must have captured six total at one point.
Also as stated above, this challenge IS counted individually. If you aren't on the platform when the generator is powered and a teammate is, it won't count for you.Filling Chests
To fill a chest, you must kill zombies around it. When it is filled it will sink into the ground. I strongly suggest having good guns and a few perks. For those who don't know yet Juggernog can be found at Generator Station 4.
The chests are found in No Man's Land. You can find a chest at these locations:
-To the left of the Excavation site (coming out of the Workshop)
-Beside Generator Station 5
-Outside the Church near the Graveyard
-Past Generator Station 4 by an MP40 wall buy
Be very cautious and keep a lookout for Giants that come through. These chests are in areas where they can step, and you don't want to get squished. The thing that makes this an even bigger pain is when Giants step on a chest it will close, and you'll have to restart the process of filling it again. Kills with the Maxis Drone, Nuke, and Electric Cherry perk do not count towards the chest.
Another thing to look out for is Panzer Soldats. If you have strong guns like Ray Gun/MkII, staffs, etc. then you'll be fine. Just keep your distance from them.
I would suggest doing the chests as early as possible as in the higher rounds the zombies will become increasingly overwhelming, and you sometimes face multiple Panzer Soldats. I would like to stress that if a Giant resets a chest, immediately start it again as you will have lots of time before the Giant comes back through.
Once you complete your fourth challenge, the achievement will unlock.
Good luck everyone :]