MW3 Zombies USB Stick Easter Egg Guide: How to Summon the Greylorm Boss

Find four USB Sticks and fight the game's hardest boss.

by Diego Perez
Image: Activision

The USB Stick easter egg in Season 1 of Call of Duty: Modern Warfare 3 Zombies summons a secret boss that will reward you with the rarest Schematics in the game if you manage to defeat it. Like all Zombies’ easter eggs, though, there are a lot of complicated steps standing between you and the Greylorm boss.

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This easter egg requires you to gather four Calibration Data USB Sticks scattered across the Urzikstan Exclusion Zone. The catch is that they spawn in random locations each match and you can’t extract them, so you have to complete everything in a single match. The boss fight itself also takes place in the Aether Storm, which makes everything even more difficult.

Where to Find USB Sticks in MW3 Zombies

To start this easter egg, head to Orlov Military Base in the northeastern corner of the map. On the second floor of a building in the H2 square of the map, there’s a map of Urzikstan with four zoomed-in locations surrounding it. Those locations are where you’ll find the UAV Towers that will give you the USB Sticks that you need.

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Image: Attack of the Fanboy

Compare these photos with your map to find the locations of the active UAV Towers for your match. Then, visit each of them and interact with them to receive the Calibration Data. It’s best to do this with a squad so you can all split up and get everything faster.

All UAV Tower Locations

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Image: Attack of the Fanboy

While only four UAV Towers will be active in a given match, there are a handful of set spawn locations that the game will pull from. You can see the possible spawn locations of every UAV Tower on the map above. When you reach Orlov Military Base, check the marked locations on the map above and compare them with the in-game photos to figure out where to go.

Related: MW3 Zombies Big Bounty Locations: Disciple, Mangler, and Mimic

How to Summon Greylorm

Once you have all four Calibration Data USB Sticks, you’ll need to find the Refractor site for the final part of the easter egg. It’s not marked on your map, but you can find it by searching for two Ammo Caches that are suspiciously close together on your map. The game never spawns Ammo Caches this close to each other unless there’s a Refractor site.

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Image: Attack of the Fanboy

Once you’ve pinpointed the Refractor site location, head there with your squad and wait. You can’t continue the easter egg until the Aether Storm expands and reaches the area. In the meantime, loot as much as you can and upgrade your gear to prepare for the fight ahead. Since the fight takes place in the Aether Storm, it’s best to have Durable Gas Masks for everyone in your squad.

Once the Aether Storm expands to the Refractor site, you’ll be able to activate the Refractors using the USB Sticks. After turning them all on, a giant red Aether Worm named Greylorm will spawn. Greylorm is the toughest Aether Worm in the game so far, beating out even Gormgant from the Act 4 Story Mission.

Related: What to Do With the Locked Diary in MW3 Zombies

How to Beat Greylorm

Greylorm has the same weaknesses and attacks as other Aether Worms, so make sure to shoot the glowing weak spots on its body to deal damage. Greylorm can also summon Mimics and other special Zombies during the fight, so be on the lookout for that. Ideally, you should have a full squad with weapons Pack-a-Punched to level 3 and all of the important Perks like Juggernog and Stamin-Up for this fight.

Once the fight is over, a Dark Aether Rift will spawn so you can immediately extract and escape the Aether Storm. Greylorm will drop a ton of loot upon defeat, and there’s a good chance you’ll walk away from this boss fight with the Flawless Aetherium Crystal Schematic, the Scorcher Schematic, or a V-R11 Case Acquisition.

- This article was updated on December 11th, 2023

About The Author

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Currently serving as an Associate Editor at Attack of the Fanboy, Diego Perez has been writing about video games since 2018, specializing in live service games like Destiny and Final Fantasy XIV. His work is featured at publications like Game Rant and The Outerhaven, but Attack of the Fanboy is home to his best work. When he's not editing or writing guides, he's yelling about Ape Escape or grinding Lost Sectors in Destiny. Plus, he has a Bachelor of Science in Telecommunication Media Studies for Texas A&M University.