The Cacodemon appears to be a large sphere of red flesh sporting several horns on top of its body. It has a single green eye and a gaping maw filled with many sharp fangs. In DOOM (2016), Cacodemons appear to have a set of limbs dangling beneath them that have atrophied to the point of uselessness.
According to their in-game description in DOOM (2016), Cacodemons are partially psionic and are driven solely by a desire to feed. When prey is sighted, they attack by spitting balls of hot plasma which burst into a cloud of narcotic mist on impact. This mist may leave the victim temporarily blinded and disoriented, but while the effect is brief, it gives the Cacodemon time to silently hover closer to the victim and devour them using its powerful jaws.
Cacodemons will float through the air idly when the player isn't close by. Upon sighting the player, a Cacodemon will move toward them at a slow pace and attack by spitting deadly balls of plasma from its mouth. These attacks can deal a lot of damage and can temporarily blind the player, but the player can prevent a Cacodemon from attacking through the use of a rapid-fire weapon such as the chaingun. With each hit, the Cacodemon suffers knockback and is unable to attack. Other weapons with greater range such as the Rocket Launcher are also highly effective.
Should the Cacodemon get close to the player, it will attack automatically by biting the player. Its bite causes a high amount of damage and can kill the player with one or two bites.