Transformation
Brute:Are a combination of multiple hosts fused together into one large being, although it's impossible to tell exactly how many bodies have been reanimated to create these monsters. They are large, hardy, and like all Necromorphs, aggressively violent. They have an armored bone exoskeleton on their anterior body for defense; however the posterior of the creature is relatively weak and devoid of defense. Brutes attack Isaac with a decimating punch, and a headbutt that can easily knock him off his feet. They are amazingly quick for their size, and you should have Stasis handy to slow them down or they can quickly run you over like a freight train. When attacked in its weak spots the Brute has been observed to contract within its armored plates to protect itself.
Dividers: Are extremely tall, thin Necromorphs that are fairly strong and hardy. Once slain,the head, arms and legs separate and become independent creatures. They are very fast and will damage and attempt to strangle you, although they are much weaker than the original Divider. Dividers tend to be loners, but it is possible to encounter a pair or a single Divider backed up by Exploders. Its components are strong when they are attacking and surprisingly weak after death. You cannot grab them with kinesis when they are surviving; but when you grab the dead ones and shoot, they blow up! Therefore they don't make a good kinesis throw.
Exploders:Are the suicide bombers of the Necromorphs. With their legs fused together in a fleshy mass, and their bodies radically twisted and emaciated (not to mention their vertically split faces), they're most likely a homage to "The Thing". Exploders appear extremely slow, but will charge at a surprising speed, so as to force you into close combat. They then attempt to clobber you with the massive pustule on the end of their left arm, which is filled with some kind of ooze. If they succeed, then the pustule will explode, killing it and causing major injuries to anything in the blast radius. Due to their "one use" nature and fairly slow movement, they most often attack in large groups, which then attempt to overwhelm you. However, this group-swarm tactic also makes them dangerous to any Necromorphs nearby, including other Exploders.
Flyers: They are not a very common Necromorph, appearing in only a few stages and in small numbers, and are not very threatening- their sole attack is to fly past the player and try to bite or slash them with their tail as they pass. A single hit will disrupt this attack and force them to fly away, and they cannot take much damage before being destroyed. This is helpful, as they have no dismemberment points, unlike any other Necromorph.
They share a similar basic body structure with the Infector type Necromorph, but their relationship -if any- with this Necromorph is unknown (However, it is possible that they are less or further mutated versions of Infectors.) . A Flyer seems to consist of an armless upper torso twisted and flayed into a shape vaguely like a stingray, topped by a partially skinned human skull and with a 'tail' presumably composed of either intertwined nerves, a dangling spinal column, or both. The human's lungs can be seen mounted on the Flyer's back, and it is possible that, similar to the Wheezers, these have been mutated into chemical production chambers and are used to help generate lighter-than-air gases that help Flyers fly. Unlike Infectors, Flyers move only through the air and possess considerable mobility and agility. This makes them quite hard to hit from a distance, and the speed with which they can dive makes waiting for them to attack the person and then shooting them, a tricky proposition.
Guardians are the result of the Necromorph infection anchoring a torso to flesh growing on the walls. One can usually tell when one is nearby when moaning, groaning, or screaming is heard. However, some have been observed as being silent until engaged in combat.
Guardian:Are sentries, set up by the Necromorphs to defend certain, often mission critical, areas. Unable to move and attack enemies unless they move up close to the Guardian, Guardians utilize embryonic spawn, similar to a Lurker in that they spit out in front of themselves which will aid in attacking detected threats.
Unlike many Necromorphs the infected human seems to retain consciousness, hence the constant moans and wails of pain, rather than simply acting as a lifeless host. The circumstances by which this occurs have not been made clear.
Immature:An immature guardian is a human torso that has just recently been attached to a wall infested with Necromorph growth and has just begun to mutate. The Immature Guardian still looks very human as it still has an unchanged head, arms and chest until the waist-down, where the abdomen is vertically split apart with the entrails hanging out. The human host is clearly still clinging onto life and will plea to the person for help in a weak and disturbingly augmented voice when alerted. Extremely weak and lethargic, the Immature Guardian is incapable of performing its matured brethren's lethal attacks and cannot host spawn. At the very most, they will play dead until approached close-up (or alerted when a light is shone in their face) where the infection will attempt to cause damage by flailing out their hosts relatively-short intestines over which the host has no control and will continue to plea for help. The creatures are 100% avoidable; the only way you can really be damaged by one is to walk up to it on purpose. Don't waste ammo on them, unless you feel like putting them out of their misery. If you use Kinesis on their body, they will moan in pain as you are trying to pull them off the wall. They will die in a matter of seconds if you constantly pull them.
Mature:A torso that has been given enough time to mutate and develop in Necromorph growth, the Mature Guardian is the most dangerous of the varieties encountered. The only remaining human feature about them is their badly mutated head, and at this point, they look more like disgusting living, breathing mounds of flesh. They will not hesitate to continuously spew out Guardian Pods when detecting a threat, and will also utilize their whip-like intestines to unerringly behead enemies that get too close to them.
Pods:Created and stored within a Mature Guardian and spat out by the Guardian upon encountering a threat through a disgusting orifice with great strength to ensure a fair distance travelled from the Guardian, these pods are sacks with a vague shape resembling an embryo. They writhe and twitch, and having been utilized as a defensive tool, they are not made to grow and survive on their own for very long.
Infectors:Look like a headless bat made from dead human material. The strange winged Infector acts as a vector for the disease, though it's not clear if it's the only one. Only attacking or defending itself when it cannot find any hosts to infect, its wings are formed by a flap of skin between the host's distorted arms and legs, with the head utterly unrecognizable, reduced to a strange proboscis. This weapon is the delivery mechanism used to infect potential hosts, which is done by enveloping the host in its wings and stabbing the proboscis into the corpse's skull to inject a yellow fluid stored in the creature's bladder. In any room with the remains of crew members, these are the beasts that should be taken down quickly before you get overrun with newly created Necromorphs. They seem to have a preference for corpses which have existing head wounds, possibly because this spares them having to crack the skull themselves; the Infector in the Morgue goes straight for the captain, with his eye-to-brain needle puncture, over any of the other corpses, and Mercer is seen to have "prepared" corpses for them by boring a hole in the center of their foreheads.
Leaper:are formed when an infected person, after about 2-4 days, starts to have visible reformation starting with the legs. The legs start to elongate, then flay and twist into a tail-like appendage. The face starts contorting, the muscles clenching and unclenching. Several jaw-like appendages emerge from the ever widening maw. The mouth no longer appears to be able to accommodate the change, and the head starts to split and burst at the seams. Almost instantly, it adapts to being perched upon its hands. They also seem to be unaware of their tail except for when they utilize it, as they drag it about uselessly on two occasions, the first being on the first encounter, as it crawls in a vent and the second being the transmission where Hammond and Kendra are attacked.
Lurker:The Necromorphs have no qualms with killing infants, and worse still, no hesitation in assimilating their bodies into their ranks. The result is a Lurker. These creatures attack using three spiked tentacles that grow out of their back either in melee when they ambush you or using them to attack at range with some sort of projectiles jetting outwards from the end of the tentacles. They are used as ranged support for other Necromorph forms and only melee as a last resort or to surprise. Lurkers are able to climb walls and stick to ceilings with suction cup-like appendages grown out of their stomachs. As a result, they're found quite often in Zero Gravity environments along with Leapers. They are commonly sighted either in small groups or with other larger Necromorphs.
Pregnantz:Are named due to the enormous sac extruding from their abdomen. They also have two scythes for attacking enemies and they are in the usual Slasher position from where human arms used to be. Other than that it doesn't have much offensive capability but despite this they will try to move in to claw you if they see him. What makes Pregnants dangerous is the spawn inside their belly: if you rupture the abdomen the amount of spawn thrown at you can quickly overwhelm him in seconds. Their weight hinders their speed so they aren't as fast as Slashers, but they can move at a brisk enough pace to out-walk you when they are determined. Initially they host Swarmers, but in later chapters of the game Pregnants appear to carry deadlier payloads of creatures including Lurkers and their enhanced versions, along with the body-part critters that come from Dividers. If the Pregnant is indeed the result of a pregnant woman, then it may be possible that the spawn produced by the Pregnant upon bursting varies on development of the baby inside of it at the time of its transformation into a Necromorph.
Slasher:Are the most common Necromorph form encountered. Their main weapons are the two blade arms coming out of their shoulders, with two pairs of grabbing arms coming out of the abdomen. They attack through pure melee combat (with the exception of the Female slasher, which can also shoot acidic spheres a small distance.), and when up close, like to grab you and bite into you're neck.
Swarmers:Are tiny Necromorphs that appear to be composed only of re-animated bits of flesh that attack in large numbers and attempt to latch onto you and overwhelm them. Swarmers often reside inside Pregnants and only come out when the stomach is ruptured, but are also encountered from time to time in independent swarms, or, bizarrely, inside boxes.
Grabber:Consisting of a seemingly inconspicuous human corpse, albeit slightly damaged, the Grabber uses the element of surprise by extending the mutated corpse's head an impossibly long distance towards the them and latch on to the person to either hold them still and distract them (not to mention disturb them), or drag them towards the Grabber's body while a serrated blade (formerly the corpse's spine) bursts out of the same orifice to kill the person. Like the Guardian, the main body appears to be incapable of movement, where in this case so much of the main body's mass has been transformed to make and store the Grabber's extremely long, muscular neck and spinal blade.
Graverobber:The Graverobber has a bear-like stance and possesses three jawless heads and pincers. It also has large, Slasher-like blades, there name implies to what they do.
Dismemberment
Take their legs out, and they'll drag themselves toward you. Shoot off an arm, and they'll use their other arm to rip into you. Nope, the only real way to take these creatures out is to completely rip them apart
Necromorphs are resilient creatures, and will never stop coming no matter how many bullets are fired into them. Countless have died due to not knowing the only true way to kill the Necromorphs: dismemberment. The only way to kill the creatures is to literally rip them to pieces; remove the head, arms, legs, and other appendages until the creature is killed.