Different types of Necromorphs (from the Wiki)

* Slasher - The most human-like of the Necromorphs, the Slasher is a mutation of a human that has recently been infected. As well as being the first type of Necromorph that Isaac encounters, they are the most diverse - the exceptionally fast-moving "Twitcher" is classified as a Slasher and the standard Slashers can be of male, female or enhanced variety. Females can spit explosive acidic spheres and have a distinct appearance. Infectors can create "Enhanced Slashers" when they infect a dead corpse - as well as having a far more intimidating black appearance, this subtype has increased vitality and armor, moves faster, deals more damage and can spit acidic spheres. Some of them will start out crawling along the ground with no legs. The Slasher is the most common of all Necromorphs. They can block melee blows unless caught off guard.

* Lurkers - Lurkers are infants that have been infected. They are quite agile and can move along walls and ceilings. They usually dash around Isaac's current area until they suddenly halt and allow their three tentacle-like appendages to rise out of their back, signaling that they are about to perform their ranged projectile attack. This consists of launching a barb from the end of a tentacle. They can also leap onto Isaac and initiate a damaging action sequence. Lurkers and Leapers are the only standard enemies that can be encountered in a zero-g environment. Lurkers also have an enhanced form.

* Leapers - A crawling variant of the Necromorphs, the Leaper faintly resembles a legless Slasher. In place of legs, the Leaper has a long and sharp tail which it uses for balance in their signature long-range jumps and for violent attacks. Their mouth is further mutated to be spread wide open and have sharp mandibles and they retain their powerful arms. All of these features are used to attack and help propel the Leaper at high speed towards an opponent by crawling or jumping. Lurkers and Leapers are the only standard enemies that can be encountered in a zero-g environment. Leapers also have an enhanced form.

* Guardian - a unique Necromorph in the sense that it cannot move from its position. This creature sticks to walls and looks very similar to a pregnant woman, but without legs. It has tentacles that can kill Isaac instantly and it can eject Lurker-like creatures from its stomach. These creatures only have one tentacle, however, and cannot move. The Guardian can be heard moaning from afar and it screeches when a creature is ejected from it.

* Pregnant - A Necromorph that resembles an infected pregnant person. Their speed is a slow pivoting type of motion, due to its obese size. They look similar to the Slashers, but their stomach area is enlarged and is hanging over their legs, although they can't spit acid like the female Slashers. Pregnants will initiate a sprint when they are about to get close to their prey, and when they are close to their enemy, they will attack with two powerful arms similar to Slasher blades. When their womb has been damaged, their torso will split open and unleash tiny Necromorphs known as Swarms. They start giving birth to two Lurkers or Divider parts as you progress through the game. Despite their appearance, they can be female or male. It is possible to kill a Pregnant without releasing the Necromorphs within by carefully dismembering limbs and not damaging the stomach.

* Infector - A distinct Necromorph that does not conform to the characteristics of standard Necromorph mutation, but causes the infection to worsen. It crawls on the ground and will fly short distances to get closer to a target. When a corpse is spotted, it will fly or crawl over to the corpse and inject a long proboscis into the head or the chest of the cadaver. When close enough to Isaac, it will initiate a grapple sequence in which it will try to inject its proboscis into the head of the player. If the player is noticed by the Infector and there are corpses nearby, the Infector will ignore the player and infect the bodies. They create Enhanced Slashers.

* Swarmer - An individual Swarmer faintly resembles a small three-legged lump of clay. They are created from a clump of dead cells. Their method of attack is to latch onto Isaac creating a 'real-time' grapple sequence where you can still shoot and otherwise fight other Necromorphs whilst slowly losing health dependent on the amount of Swarmers on Isaac's back. They are thrown off in the same method as any other grappling enemy. A single Swarmer is easy to kill in a single hit. However, as the name suggest, this type of Necromorph tends to come in a large swarm which is capable of killing Isaac easily if they all latch onto him. Using their small legs to roll around, they are slow and easily dispatched if caught from a distance. They can be found wandering in a large horde or can be released from an incorrectly killed Pregnant.

* Divider - A curious mutation, this Necromorph has the ability to separate itself. It is taller than an average Necromorph and slightly more resilient. Every dismembered part of this Necromorph, however, has the capability to become a fast-moving individual organism that causes small amounts of damage, but is very difficult to target. When the head is separated, it is capable of causing a grapple sequence where it will lower Isaac's health until you throw it off.

* Brute - A large heavily armored Necromorph that is impervious to any damage to its front. The thick plates of bone armor that shield the Brute from damage also cover its arms and fists. The only unprotected area is on its legs and back. It attacks using its heavy spiked hands or it will charge and knock the player over. When the legs are severed, the Brute will begin to launch acid bombs from its stomach until it is killed. Brutes have an enhanced form.

* Twitchers - Twitchers are first encountered on Chapter 9 of the game. They were created from the dead bodies of the marines onboard the USM Valor which was to rescue the trapped inhabitants of the USG Ishimura. However, the infection soon killed these marines, but the recombination process had a strange effect on them. The marines all had built-in stasis units in their armor. When the infection corrupted them, it merged the stasis units with their flesh, reversing the original effect. Twitchers can move incredibly fast and can hone in on Isaac at a long distance in only a few seconds. They are, essentially, a variant of the Slasher but much tougher. These Necromorphs are the most human-like. When they have lost both their legs, they move around on their arms at the same speed as a running Slasher. They are called Twitchers because while standing still, they have fast, jerky and erratic movements. Watch out for these creatures.

* Thrashers - A large spider-like Necromorph that spits out acid when provoked. If you are unfortunate enough to provoke one of these, you will need to shoot it in the head to kill it.

* Exploders - First encountered in Chapter 6, the infection has resulted in the legs being fused and the head being split vertically. A large, yellow sack extends from the left arm, which serves as a cane and a weapon. Targeting the sack will cause an explosion, killing the exploder and anything around it. It will approach Isaac and attempt to swing the sack-bomb at him and intentionally destroy itself to kill him. This is very rarely survivable.

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