There are pieces of technology and hazardous equipment all over Blackreef in Deathloop. You’ll want to avoid sensors and turrets as often as possible, typically using your hackamajig to turn them over to your side, tipping the odds against the many Eternalists hunting you down. There’s also field nullifiers, and these are going to be bad for you, the Visionaries, and Julianna when she comes looking for you.
A field nullifier is a device that looks just like a turret, but instead of filling you with bullets, it’s going to give out an area of effect ability that turns off Slabs. So when you’re in this field, your Slab won’t work, and you’ll be stuck without it. These count both the Slabs you’re going to earn by defeating the many Visionaries on the island, and your Reprise, which allows you to revive a set amount of times.
Even if you attempt to hack and use a field nullifier, it will still block you. You’re better off tossing it near a Visionary that’s giving you trouble or setting up a trap for Julianna. If she finds it before you do while she’s hunting you down, and she’s a player, you can bet she’s going to try using it to her advantage. Thankfully, with your hackamajig in your hand, you should be able to shut it down, but you want to hack it first before she guns you down. You’ll know the effect is currently active by the aura around the outside of your HUD, and your Reprise ability on the left side is gone.
The field nullifier is just like a turret. When not deployed, you can pick it up and place it somewhere else, remotely activating it when you’re ready to use it.