Black Dweller

A  is one of the monster types you'll encounter. It spits triple-chained acidic bile projectile when attacking, from a medium range. They have very strong defense making harder to deal damage to them with low-damage weapons. Gatling Turrets can be effective against them if there are several of them and stays long enough in front of them, but using Heavy Turrets or better turrets is safer, and water can be used to slow them down greatly.

Location
You can find Dwellers in the Stone Caverns, and inside the Volcano