A Full Breakdown of the Serum Puzzle Challenge in BO7 Zombies

Among all the objectives tied to the Ashes of the Damned main Easter egg in Call of Duty:Black Ops 7 Zombies, the Serum quest stands out as one of the most demanding. Players must track down six rare biological components scattered across the map, many of which are locked behind specific upgrades, enemy conditions, or round requirements. Once collected, those items must then be used to solve a dangerous laboratory puzzle under lockdown conditions.

All Serum Component Locations in Ashes of the Damned

Serum Component 1:Powder of the Forgotten

To obtain this item, you'll need Wisp Tea and the Necrofluid Gauntlet.

Wisp Tea can be purchased at Zarya Cosmodrome, or earned for free by completing the Twins Easter egg at Vandorn Farm. Once the tea is active, head to the Tailor Shop in eastern Ashwood, located just past the Vulture Aid perk. Inside, you'll find an enchanted mirror.

Simply standing close to the mirror while Wisp Tea is active will cause it to crack and shatter. Afterward, equip the Necrofluid Gauntlet and shoot the broken mirror. This interaction causes the Powder of the Forgotten to fall to the ground.

Serum Component 2:Widow Lantern

Travel to Blackwater Lake and enter the nearby cabin. Head downstairs into the kitchen and open the sink cabinet along the south wall to retrieve a Jar of Spores.

Next, bring the jar to Vandorn Farm. Just outside the main gate, you'll see a deceased horse overtaken by fungal growth. Interact with it to plant the spores. After three full rounds, the growth will mature, allowing you to collect the Widow Lantern.

Serum Component 3:Mysterious Limb

This component is tied to Zursa, the zombie bear Elite enemy, which begins appearing from Round 16 onward.

To secure the drop, 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, grab the Freezer Key, and complete the upgrade process in Ashwood.

Once Zursa spawns, weaken her using conventional weapons. When she's low on health, finish her off with the Beam Attack. If done correctly, Zursa will explode and drop the Mysterious Limb.

Serum Component 4:Ravager Eyes

Ravagers are agile, quadrupedal enemies that can appear randomly or during Max Ammo rounds. When one spawns, lure it toward a Saw Blade trap, such as the one positioned outside the Vandorn Farm Barn.

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 step also requires Ol' Tessie's Abomination Head upgrade.

Drive Ol' Tessie along the connecting roadways and watch for purple-glowing plants, which spawn randomly across the map. Once you spot one, use the Beam Attack to destroy it. Doing so will cause the Hoard Husk Chunks to drop.

Be careful when exiting Ol' Tessie after collecting this item—enemy aggression in these areas is significantly higher.

Serum Component 6:Human Bones

Head to the Barn at Vandorn Farm. You'll need both a Combat Axe and a Molotov, both of which can be acquired at no cost.

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.

Throw the Combat Axe at the corpse's right foot to knock it down. Once it hits the ground, toss a Molotov onto it. After the flames burn out, the Human Bones will be available to pick up.

Once all six Serum components are collected, make your way to Yuri's Lab, located southwest of Zarya Cosmodrome. Inside, you'll find six bowls arranged around the room, each corresponding to one of the items you've gathered, along with a chemistry station in the center.

Begin the puzzle 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. When visibility returns, three Pigpen cipher symbols will appear on the chalkboard.

These symbols indicate the exact order in which the remaining bowls must be activated—from top symbol to bottom symbol.

During the lockdown phase, natural health regeneration is disabled. The only way to heal is by using the Necrofluid Gauntlet siphon ability, which drains health from zombies by firing and reloading. Proper crowd control and careful timing are essential here, especially for solo players.

Successfully activating the bowls in the correct order and surviving the lockdown will complete the Serum puzzle and advance the main Easter egg.

Practicing the entire Serum sequence in Black Ops 7 Bot Lobbies is strongly recommended. This allows players to rehearse the more punishing steps—such as Zursa's Beam kill or the lab lockdown—without the pressure of public matches. Many experienced players even use bot lobbies specifically to master Easter egg mechanics before attempting full runs.Whether you're new to Black Ops 7 or pushing advanced techniques, MMOexp buy CoD Black Ops 7 Bot Lobbies provide a stress-free environment to learn, practice, and improve at your own pace.

Although the Serum quest initially feels overwhelming, it becomes one of the most reliable sections of Ashes of the Damned once you understand each requirement. With preparation and patience, this complex puzzle transforms into a consistent and repeatable victory.