One of the most challenging objectives in Call of Duty:Black Ops 7 Zombies takes place during the Ashes of the Damned main Easter egg. The Serum puzzle requires players to locate six unique biological components scattered across the map, many of which are locked behind specific upgrades, enemy conditions, or round requirements. Once collected, these items must be used to complete a high-risk laboratory challenge that tests both survival skills and puzzle awareness.
All Serum Part Locations in Ashes of the Damned
Serum Component 1:Powder of the Forgotten
This component requires two items:Wisp Tea and the Necrofluid Gauntlet.
Wisp Tea can be purchased at Zarya Cosmodrome, or obtained for free by completing the Twins Easter egg at Vandorn Farm. Once the tea is active, travel to the Tailor Shop in eastern Ashwood, located just to the right of the Vulture Aid perk.
Inside the shop is a mirror that reacts to Wisp Tea. Simply stand close to it while the effect is active, and the mirror will shatter. Afterward, equip the Necrofluid Gauntlet and shoot the broken mirror to cause the Powder of the Forgotten to drop.
Serum Component 2:Widow Lantern
Make your way to Blackwater Lake and enter the cabin nearby. Go downstairs into the kitchen and open the sink cabinet along the south wall to retrieve the Jar of Spores.
Next, bring the jar to Vandorn Farm. Just outside the main gate, you’ll find a dead horse covered in fungal growth. Interact with it to plant the spores. After three full rounds, the spores will fully mature, allowing you to collect the Widow Lantern.
Serum Component 3:Mysterious Limb
This item is tied to Zursa, the Elite zombie bear enemy that begins spawning from Round 16 onward.
To obtain the Mysterious Limb, Zursa must be killed using Ol’ Tessie’s Abomination Head Beam Attack. First, unlock the Abomination Head upgrade by visiting Reba Diner at Exit 115. Defeat the Cook zombie, collect the Freezer Key, and complete the Ol’ Tessie upgrade process in Ashwood.
Once Zursa appears, weaken her with standard weapons. When her health is low, finish her with the Beam Attack. If done correctly, she will explode and drop the Mysterious Limb.
Serum Component 4:Ravager Eyes
Ravagers are fast, four-legged enemies that can spawn randomly or during Max Ammo rounds. When one appears, lure it toward a Saw Blade trap, such as the one located outside the Barn at Vandorn Farm.
Activate the trap for 2,000 Essence and allow it to kill the Ravager. Upon death, it will automatically drop the Ravager Eyes.
Serum Component 5:Hoard Husk Chunks
This component also requires Ol’ Tessie to be equipped with the Abomination Head upgrade.
Drive Ol’ Tessie along the interconnected roadways and look for purple-glowing plants, which spawn at random locations. When you spot one, use the Beam Attack to destroy it. Doing so will cause the Hoard Husk Chunks to drop.
Be extremely cautious when exiting Ol’ Tessie after collecting the item, as zombie aggression in these areas is significantly increased.
Serum Component 6:Human Bones
Travel to the Barn at Vandorn Farm. You will need both a Combat Axe and a Molotov, both of which can be obtained for free.
The Combat Axe can be found in the Reba Diner kitchen, while Molotovs can either be crafted inside the Barn or picked up near Ol’ Tessie’s garage. Inside the Barn, locate the hanging corpse in the center of the room.
Throw the Combat Axe at the corpse’s right foot to sever it. Once it drops to the floor, throw a Molotov onto it. After the flames extinguish, you can collect the Human Bones.
After gathering all six Serum components, head to Yuri’s Lab, located southwest of Zarya Cosmodrome. Inside the lab, you’ll see six bowls arranged around the room, each holding one of your collected items, along with a chemistry station at the center.
Begin the sequence by interacting with the Powder of the Forgotten, which is placed in the fifth bowl. This triggers a lockdown and fills the room with smoke. Once the smoke clears, three Pigpen cipher symbols will appear on the chalkboard.
These symbols indicate the order in which the remaining bowls must be activated, starting with the top symbol, followed by the middle, and then the bottom.
During the lockdown phase, health regeneration is disabled. The only way to recover health is by using the Necrofluid Gauntlet siphon ability, which drains life from zombies when firing and reloading. Survive the lockdown while activating the bowls in the correct order to complete the Serum puzzle.
Practicing this entire process in Black Ops 7 Bot Lobbies is highly recommended, particularly for solo players. Bot lobbies allow you to rehearse timing-sensitive steps—such as the Zursa kill or the lab lockdown—without the added pressure of public matches. Some players even opt to buy CoD Black Ops 7 Bot Lobbies specifically to master Easter egg mechanics safely.
While the Serum puzzle may seem overwhelming at first, understanding each requirement turns it into one of the most reliable and repeatable steps in Ashes of the Damned. With preparation and patience, it becomes far less intimidating and far more rewarding.