As part of the main campaign mission for BO6 Zombies Reckoning, you get a series of tasks that will take you to the end goal of fighting the final boss. Following along with the storyline will take you to the T1 Mutant Research Lab, which is accessible very early in the campaign. Over here, you need to locate a keycard to gain access to the box containing a syringe, then use it to get the Fowler Mutant Injection. This guide will detail the steps to acquire the injection in BO6 Zombies.
Fowler-Mutant Injection In BO6 Zombies Reckoning

The keycard is located within the T1 Mutant Research Lab and drops from defeating the Geneticist zombie. To get to the Lab, when you spawn into T1 Project Janus Reception, take the elevator on the right to get up. Follow the directions to reach the Research Lab, then wait around to find the Geneticist zombie spawn. This is a random zombie spawn and may appear at any level, so keep your eyes peeled for them.
Once you spot them approaching you, kill them and get the Keycard drop. To use the Keycard, head inside the T1 Mutant Research Test Area and make your way to the cloning center where Richtofen’s family is located. Use the keycard on the fridge opposite the clones to pick up the DNA Vial.
Syringe Location and Use BO6 Zombies Reckoning

Head out of the Test Area and back to the T1 Mutant Research Lab. Walk across the center of the area to find a cloning tube with a Mangler inside. Right beside the Mangler clone is a centrifuge; unlock it to get the Syringe. Now, you need to get a Blood Sample. For this, you need to unlock the Pack-A-Punch within T2 Sublevel 10. After activating and repairing the Particle Accelerator, jump up and walk across the Accelerator’s beam.
Floating on the beam is a dead zombie, try to knock it off the beam so it falls to the floor. Walk up to the corpse and interact with it to get the Blood Sample. Head back to the centrifuge in T1 Mutant Research Lab and plop the now-filled syringe back in. This will summon the Fowler-Mangler, defeat it to get the Fowler-Mutant Injection.
How to Use the Fowler-Mutant Injection

For the final step, make your way to T2 Dark Entity Containment and head up the stairs on the right. There is a set of doors here locked behind a scanner. Use the Fowler Mutant Injection and interact with the scanner to gain access to the room beyond. There is a portal that will take you to the T2 Teleportation Lab, and within this lab is a computer terminal that requires the code.
Check out our guide on obtaining the Teleportation Lab Code to complete this part of the campaign mission objectives in BO6 Zombies Reckoning.