It resembles a Bloodsucker, with the same body structure, mouth tentacles and lambent eyes, but has irregular patches of dark fur on its skin, it's skin is also slightly greenish and moss-like compared to a regular bloodsucker.
Like its more common relative, the marsh creature possesses powerful optic camouflage which allows it to turn almost invisible. However, the marsh creature's methods of hunting and combat are distinctly different from that of Bloodsuckers. Where bloodsuckers use their claws to swipe and slash at prey, the marsh creature instead chooses a specific target, pins it down against the ground and then leaps away with the unfortunate victim, giving other enemies little time to react. Once in safety, the marsh creature feeds on its captured prey and then retreats.
The marsh creature's main habitat is the Great Swamp where it constantly travels around the area looking for prey, but it can also be sighted in areas that border on the swamp, such as Agroprom. It is scripted to appear on the player's first journey to Agroprom, where it attacks and eats one of the members of the Duty patrol.thumb|300px|right|The Marsh Creature's scripted appearance at Agroprom.
- Its name stems from the fact that the creature can first be encountered in the Great Swamp.
- It is unknown whether the marsh creature is an entire sub-species of Bloodsuckers, or if it is actually just a single nomadic creature.