The Slinger appears to be a human mutated with the Uroboros virus. The human base is evident in the leg and abdomen section. The upper torso stops at the rib cage and opens up into a large arm used to throw explosive parasites at the player. These parasites cause splash damage. The parasite then grows back, and the animation reveals the Uroboros tentacles coming out of the arm.
The Slinger is first encountered in Episode 2: Contemplation in Barry and Natalia's campaign. It normally will appear accompanied by multiple Revenants. It will rear it's arm back, like a quarterback, and throw a parasite at the player. It deals moderate damage upon a hit and will blind the player. This is capable of hitting both characters at once. It's a weak point is the big orange blob in its face.