Leeches are legendary mutants that, according to the Stalkers, reflect the corruption and danger that prevails in the Zone. There have been very few Stalkers who have encountered this type of mutant on their way and have lived long enough to tell about it, most of the people in the Zone have never had a chance to see Leeches. These mutants have a habit of looking for darkened hiding places where they sleep and store food. Interestingly, they sleep standing up, with their heads lowered, it is worth noting that it is very easy to wake them up.

Leeches are natural night hunters, they are characterized by very high resistance to damage and speed, they are one of the fastest mutants in the Zone, which, combined with optical camouflage and powerful claws, makes them extremely deadly individuals. Additionally, they move practically silently, so they can quickly sneak up on their victims and kill them immediately. It is worth knowing that Leeches are the most vulnerable to attacks while using camouflage, if the Stalker manages to hit the Leech while it is invisible, it will deal the most damage to it. Leeches are permanently invisible when they sense a threat, they only become visible when attacked.