Bloodsuckers are a rare type of mutant usually found in the deeper areas of the Zone, often underground. They seem vaguely humanoid, with a hunched stance and height similar to that of an average person. Their eyes are lambent and their mouths are surrounded by several powerful tentacles used for feeding on blood.
The Bloodsucker is a semi-legendary creature, often used by Stalkers as a symbol of both the dangers and corruption of the Zone. This status has been achieved thanks to the species’ relative rarity, as well as the fact that few humans who encounter Bloodsuckers survive to tell of it.
Bloodsuckers often make lairs, in which they will dwell while resting or storing their kill for later consumption. They also sleep standing up but aren't known to do so heavily, as even something as quiet as a light footstep will instantly awaken them.
Bloodsuckers are not tremendously resilient. However, they are one of the fastest enemies in the game. This, when combined with their ability to turn invisible, the fact that they don't create any sound while resting or walking, and their incredibly damaging attacks (their claws ignore all armor) make them extremely dangerous opponents, especially when the player is distracted.
Perhaps the most peculiar thing about Bloodsuckers is their optic camouflage, which allows them to temporarily become almost invisible to the naked eye. However, Bloodsuckers are at their weakest when cloaked. Bloodsuckers will often engage their camouflage upon discovering prey, and then become visible again when they are close enough to attack. Bloodsuckers will usually bite into the corpse to drain it of blood, which is what gave them their name.
Curiously, each individual has evidence of severe decomposition – bits of flesh appear to be necrotizing and sloughing off their body. All specimens seem to lack skulls as the skin on their heads peels away in areas, exposing the brain underneath. This may explain their lack of any sign of sentience or reasoning capability. While this trait isn't present in most of the Bloodsuckers in Clear Sky, a handful from Shadow of Chernobyl express this and is a global trait in Call of Pripyat, perhaps suggesting that the bloodsuckers in the area are evolving, or that the species as a whole is afflicted with a genetic disorder. However, it may also be a sign of aging.
How exactly Bloodsuckers reproduce – and how there are so many only a few years after the first Emissions – is one of the larger mysteries of the Zone.
The most effective tactic for destroying these creatures changes depending on where they are encountered. If you are in a location with some light but in close confines, such as the "bloodsucker house" in Dark Valley, try to use a pump-action shotgun like the SPSA-14. Or, if you are bold, you could try to attack the bloodsucker with a knife - once it's close, but still cloaked, slash at it quickly with your knife. Usually, one hit will kill them. It may take more than one try, as this is a difficult skill to master, but once mastered, it's extremely effective. Note that this strategy is not recommended if you don't have good enough armor, and should only be attempted without armor when you have mastered the skill, as you may fail several times at first. It's recommended that you practice while wearing an Exosuit, as one will protect the player from the bites quite well.
Slug ammunition is also effective at taking down Bloodsuckers from a relatively safe distance, though buckshot is preferable at close range. If you are in a very open area, assault rifles are far more preferable due to the unpredictable spread of shotguns, and the assault rifle's ability to fire at range. An accurate rifle and an endurance-increasing artifact such as Moonlight, Snowflake, Sparkler, or Flash will allow you to simply outrun the bloodsucker, possibly luring it into anomalies or friendly troops. Elevation and distance are the most effective endurance to bloodsuckers; their clawed hands have lost their ability to form a fist and they cannot climb nor jump onto vertical structures more than 1.5 meters tall. In addition, they also seem to be afraid of heights, as if the player is on an elevated, but exposed position such as a spiral staircase in the watchtower at Bloodsucker Village, these mutants will attempt to pursue the player up the staircase before running back down and outside again. Bloodsuckers also don't like being exposed; if the player surprises one outside, and is more than about 30 meters away, the bloodsucker will become startled and dash toward the nearest enclosed space, remaining inside until the player enters the house. If the player doesn't enter the house, nor come near it, the bloodsucker will either remain hiding for several hours or wait until the player is stationary for a few minutes. If the player is able to spot a hiding bloodsucker that ran inside a house and is able to harass it with gunfire, the creature will become confused and scared, running wildly around in circles. It's best to avoid scaring bloodsuckers as they are easily at their most aggressive when afraid. This is the best possible situation for a stalker with a scoped weapon, as the creature's cloak becomes less effective the faster it moves, and its telltale eyes give an excellent indicator of where to aim.
The most effective way of killing a bloodsucker is the element of surprise. If the player discovers a bloodsucker who is unaware of his presence, a wonderful opportunity is presented: If you manage to headshot the bloodsucker, with any weapon, it will be an instant kill. This is a very rare opportunity, but it is well worth the investment or time in finding a weapon which can reliably deliver accurate kills.
Finally, it's encouraged for the player to use his binoculars as much as possible. In addition to identifying human enemies, the binoculars can also spot and highlight bloodsuckers that are hidden behind foliage, and sometimes even those who are cloaked or hidden by darkness. Binoculars are immensely useful tools and should not be ignored.
Much like most mutants; should enough damage be dealt with a bloodsucker, it will start limping and move at a largely reduced speed, which is referenced with the mutant clutching his stomach and moving in a staggered fashion, making it easy to get away to deliver the killing blow to one. Gravely wounded bloodsuckers are also more susceptible to retreating from a fight.
Early on in the game, bloodsuckers can be immensely difficult to defeat due to both the low rate of fire of most weapons and the lack of high-damage weaponry available. Bloodsuckers can be one hit killed if shot in the back of the head whilst unaware; this can be extremely risky to pull off, but very gratifying. A very short burst of approximately 4 rounds from a machine gun (RP-74) will instantly put down a Bloodsucker. In Shadow of Chernobyl, the Bloodsucker can actually be spotted with a snappy perception, if you are prepared to meet it (try it out at one of Strelok's stashes). When seen through a cloaked bloodsucker the background is blurred in an almost water-like reflection which is highly visible when they move. Also, two glowing white spots can be seen in the air – which are obviously their eyes. Do not doubt yourself upon seeing them; there are no other enemies in the game that have the same glowing eyes. Fire in that direction, preferably just above the eyes for maximum damage per shot.
Shadow of Chernobyl
Bloodsuckers are first encountered in the Agroprom Underground, where one will attack the player during his first trip to infiltrate the military outpost. After that, they make rare appearances above ground, but tend to avoid confrontation. This is fortunate for Stalkers, as they are easily the most dangerous mutant in the original game, aside from the Pseudogiant. They can be shot and damaged at any time, unlike the variants that appear in Clear Sky, and like many other mutants, their greatest weakness is the inability to climb over even a knee high barricade. On later stages of the game, bloodsuckers commonly appear at the Wild Territory (Rostok), Military Warehouses, Dark Valley, and can be rarely seen in Cordon during later parts of the game. Strangely, there is one particular bloodsucker at the Dark Valley which is in the middle of nowhere, near the east end of the map. There is a mission available - Kill the Bloodsucker in the Dark Valley - to kill this particularly unusually situated mutant. A quartet of bloodsuckers occupy Lab X-19, inside the Brain Scorcher.
Bloodsuckers are almost identical in both appearance and behavior. The only notable difference is that they don't take damage from attacks while invisible in Clear Sky. Also, they have a tendency to travel in packs, making them even more lethal and all the more frightening. A second 'species' of Bloodsucker, known as the Marsh Bloodsucker, makes appearances throughout the Great Swamps – they work alone and tend to be extremely disruptive during the faction war, as one hit from them will bring down a squad member before the bloodsucker tosses the corpse into the swamps to feed. The rest of the squad will normally go stationary expecting an encounter, and because of this, the Marsh Bloodsucker can often wipe out a whole squad because they refuse to get out of the area.
Also, in Clear Sky, they may sometimes threaten the player if the player gets too close – they will roar and normally do this after wounding their victim.
Call of Pripyat
In Call of Pripyat, bloodsuckers are most prevalent in Zaton as all three types can spawn, and Marsh Bloodsuckers appear in Yanov usually near the swamp rim. Very rarely, a third, much more dangerous variant may appear in either location (or in Pripyat itself). This new third species is significantly more powerful and has more resistance to damage. While this new species still possesses the ability to cloak, it's often shoddy and obtrusive compared to the Forest or Marsh Bloodsuckers, making them stand out – for example, appearing as bricks on grass or dirt. Unlike Clear Sky, bloodsuckers can be damaged even while cloaked and, aside from the new species, aren't nearly as dangerous to regular stalkers, who can sometimes fare well against a pair of them. To compensate, bloodsuckers have gained improved optic camouflage. A cloaked bloodsucker's outline can no longer be seen at long range and their eyes can only be seen when they're at close range, prompting the player to be extremely alert and use lightning reflexes to overpower a bloodsucker. The terrain can also be used to detect bloodsuckers as they will splash water when walking on it. The crosshair, if enabled and dynamic, may turn red to indicate the presence of an enemy when aimed at a hostile bloodsucker, even if it is invisible.
They are one of the creatures scripted with a new attack, one which automatically activates if the player exposes their back to the bloodsucker, but can also happen if the player is struck full-on by a charging one in the front. The mutant grapples onto the player and sucks blood from the player while other mutants get free shots – in a pack this often leads to death. The player loses health and a significant portion of their stamina bar to the bloodsucker, who gains a small amount of health in return.
Unsurprisingly, bloodsuckers feature heavily in the mission "Bloodsucker Lair", in which the player must find a way to wipe out a nest of Bloodsuckers that have been preying on Stalkers in the Zaton region. They can also occasionally be seen in the distance whilst traveling in Zaton and Yanov.
Like many other creatures, bloodsuckers now have a changed behavior when attacking. Instead of recklessly charging like in the other games, it will cloak when threatened and try to gain proximity while invisible on a victim. A bloodsucker will then briefly reveal itself before slashing or even grappling the player with its tentacles. It often uses "guerrilla" attacks by circling around before attacking once every couple of seconds to which it repeats. The only way to pinpoint on a bloodsucker's position when cloaked is its heavy breathing or, in one instance, its position on the minimap. However, if fighting it near or in water (such as in the swamp during a mission given by Trapper), one can see the ripples in the water caused by its movements, giving away both its position AND direction of movement, even while it is cloaked.
- In SoC and CS, there is another variation of the standard bloodsucker. However, this variation, called a "sub-bloodsucker" in the PDA, has only aesthetic differences. The sub bloodsucker has a different PDA image, darker skin, and larger pores on its face. These kinds of bloodsuckers don't appear as common as the other variant. A stuffed sub-bloodsucker can be seen in Clear Sky at the Inquisitor's zoo, which is the one next to the wall opposite of the windows.
- In earlier builds, bloodsuckers used sounds borrowed from the zombies in Return to Castle Wolfenstein.
- The Bloodsucker's head in the S.T.A.L.K.E.R. franchise may be inspired by the Centaur's design from the original Fallout games.
- The Bloodsuckers are very similar to Reapers from Blade 2.
- The Bloodsuckers also appear to resemble illustrations of Cthulhu, from H. P. Lovecraft’s novella The Call of Cthulhu by both their physical appearance and their effects on the mind of whoever looks upon them. Cthulhu is a possible inspiration for the bloodsucker (The illustration can be found in the gallery). In the book, it's stated that Cthulhu can cause mental illness, mass madness, insanity, and strange dreams on any individual. Moreover, there's a cult of Cthulhu in the short story, who perform dark rituals in his name. Although these mind-affecting capabilities weren't implemented into the game, Cthulhu's physical appearance likely influenced the Bloodsucker
- The Bloodsuckers may also be inspired by Mind Flayers from the Dungeons and Dragons franchise, as they are both hairless humanoid creatures with tentacles protruding from their mouth
- In S.T.A.L.K.E.R.: Clear Sky, there is a bloodsucker programmed to follow the player no matter what. He spawns during a rare artifact retrieval mission in the Army Warehouse. Of course, killing the creature solves this problem.