Scientists appear to be normal human men wearing a lab coat, grey undershirt, red and black striped tie, black pants, brown shoes, and a mask featuring slits for the eyes and a metal mouth guard. Each one is seen brandishing a syringe filled with an unknown substance. It is suggested the Scientists are responsible for creating many of the augmented units in The Military, such as The Experiments and the Welders.
Scientists will emit a short laugh upon spotting a player. They will then proceed to chase the player down at a relatively fast speed. If a scientist manages to catch up to the player, they will attempt to stab them with their syringe. The attack from a syringe is enough to cut a player's health in half or worse on harder difficulties, though Scientists themselves are weak enemies. In levels where multiple Scientists are around, such as E2M5: The Escher Labs, the player will need to keep an ear and eye out for ambushing Scientists. Their shoes make a distinct sound when they walk, giving away their position.
Since Scientists are weaker enemies with a health pool of 175hp, two blasts from the Shotguns or continuous Assault Rifle fire is enough to bring one down. Scientists usually appear in groups and alongside other enemies like the Possessed Soldiers, so targeting them first is a good strategy. Due to their glass-cannon mechanics, the player will need to be on their toes when they hear a Scientist's laughter.
- The Scientists bear strong resemblance to the scientists from the Black Mesa Research Facility in Half-Life.
- Possibly inspired by Dr. Decker, the villain from the 1990 dark fantasy film Nightbreed, as their heads look slightly similar to Decker's mask.