Warning: Make sure you are playing in Classic because this Achievement can't be unlocked if using any modifiers.
(still being updated)1. Unleash the Spirits -
You will need to build the Spectral Shield, with it absorb 3 Spirits and then Spirit Blast (press L1 then hold L2 and press R2) the power box on the Roof to unlock the Pack-a-Punch Machine.
Build Spectral Shield Guide:
Unlock Pack-a-Punch Machine:2. Shock and Denial -
You will need to obtain the Spoon for this step. Once you have the spoon head to the Warden's House, melee the left wall at the top of the staircase. You will need to wait until Round 17, as you need a Brutus that can EMP slam, return to the wall in the Warden's House when you have the Brutus. Allow Brutus to get close enough until a EMP slam is performed. If done correctly, the wall will fall revealing the Warden's Ritual Room. Enter the Ritual Room, activate the lever next to the electric chair and obtain the red orb on a table across from the electric chair.
If on round 17 Brutus did not spawn, you can input 666 into the number pad (press Square) in the Citadel Tunnels to spawn one.
Obtain the Spoon:
Unlock the Ritual Room:
3. Pain and Guilt - Head to Richtofen's Laboratory and place the red stone into the map. Next, activate the Kronorium that can be found in the same room, a bird will spawn and you must find it around the map 4 times.
For this step it would be recommended to upgrade the Spectral shield. To do that, use the mystery box until you get the lock, then shock it with the key until it turns blue, then throw the hell's retriever/redeemer at it and now you can hold 4 Spirit Blasts.
The bird can be found in almost every area of the map, the easiest way is to find it by the sound it makes.
Once the bird has been located, Spirit Blast it (press L1 then hold L2 and press R2) using the Spectral Shield. Repeat this process a total of 3 times, once per round.
Once you need the 4th bird, you will need to find a glowing sparkle around the Showers, China Alley and the Docks, once you hear the warden crying along with the bird, using the shield try to find the glowing sparkle.
You will now need Zombie Blood (for the 4th bird only) and to get it input the number 872 in the number pad, run to the location that you found the sparkle/sound and use the spectral shield vision to see the bird, and throw the hell's retriever/redeemer at it.
If done correctly, it will drop the Kronorium. If you fail to find the bird in the zombie blood, you will have to end the round and try again.
Pick up the Kronorium, then head to the Warden's Ritual Room and place it on the corpse in the electric chair.
Obtain the Hell's Retriever:
4. Anger and Bargaining - Using the Spectral Shield, reveal the 3 numbers on the pages of the Kronorium. Navigate to the number pad and enter those 3 numbers. If done correctly, the Lighthouse will be "aiming" toward a location in the map where a portal can be seen using the Spectral Shield vision, you will need to Spirit Blast the portal to activate it.
Each portal corresponds to a challenge, you must complete 5 portals and each portal has different objectives/challenges. If you fail a Challenge a new set of numbers will be generated on the Kronorium in the Warden's Ritual Room.
Once all 5 Portals are complete, head to Richtofen's Laboratory and place the red orbs in the map. Next, all players must head to the Warden's Ritual Room and stand near the corpse in the electric chair. Electric beams will form from each player to the corpse, the Summoning Key will now appear above the Kronorium and a cutscene will start.
Once the cutscene is over all players will be locked in cells but the blue bird from the earlier steps will return and set the players free from the cells.
Once you are out of your cell make sure you equip a Spectral Shield and retrieve your weapons from the bag.
Follow the bird out of the prison back to the West Grounds. An in-game cutscene will begin with the ghosts fighting the Warden. After the Warden flies away, obtain the orb and place it on the map in Richtofen's Laboratory. The map will begin to burn, opening a previously sealed door in Richtofen's Laboratory. Warning: Make sure you are ready for the Boss Fight by having all Perks and Pack a Punched Weapons and Blundergats.
All players must go to the top of the stairs and stand on the dimmed lights causing them to brighten. All players need to hold Square to open the door in order to enter the boss fight.
Boss Fight - You must 1st Kill Zombies until you see the warden arrive. Once the Warden has began his attacks, stand in the red zones and shoot the red glowing orbs. After breaking the orbs, shield blast the Warden. Then shield blast the orb on the machine. Repeat this 2 more times. On the 3rd stage Richtofen will need to activate the machine so he can sit in the chair. That player will get a cutscene, then that player will need to return to the boss fight area by standing on the dimmed light and hold Square to open the door.