- John Carver: "Are you sure this is working? I think we're just pissing it off!"
- Isaac Clarke: "No, it's working, keep going!"
- —John Carver and Isaac Clarke while fighting the Nexus
The Nexus is a Necromorph hive mind variant encountered on Tau Volantis. Much like the Hive Mind encountered on Aegis VII, the Nexus serve as ground commanders for lesser Necromorph forms, telepathically broadcasting Marker signals and coordinating infestations.
In order to continue progress in the mission in stopping the Markers, Isaac has to activate nerve clusters inside a live Nexus' body cavity, that are used to tracking down the Alien Machine. However, the Nexus is irritated by this and attacks Isaac, Carver, Norton and the Unitologists who previously attacked the crew.
Isaac and Carver successfully manage to take down the enormous beast, with it finally collapsing to the ground, dead.
The Nexus are gargantuan crustacean-like Necromorphs of the same hive mind sub-species as the one encountered on Aegis VII. Although only the upper body section is shown during the boss fight with the Nexus specimen 001, the rest of the body is shown on a table showing its external anatomy. It appears to be created from at least one corpse belonging to the extinct alien species native to Tau Volantis; its "head" resembles the skulls of the alien skeletons seen later in the game, hence the difference between the two giant Necromorph encountered in the series.
The Nexus Necomorphs possess four known limbs which they use to attack with. The head are very mantis like and have four eyes separated by large fleshy openings down their crowned foreheads. Their vertically split mandibles, when open, reveal two large claws and five large pustules which surround their mouths. The chest cavities open to reveal a large glowing pulsating sac similar to the Hive Mind in Dead Space. They also have 4 similar appendages to the Aegis hive mind on its back. It is unknown what the purpose of these are but it is possible they act as "antennas" that broadcast the Marker signal to the other Necromorph pawns and also receve it from the Markers and the Moons. During combat, they use four of their long limbs to attack while two blade like arms rest behind the head. They attempt to smash their victims or suck them inside their mouths, down into their stomachs where the Nests that are located will take of them, if they aren't drowned in the liquid that is in the stomach.The Nexus have hollow internal chambers which are covered in Corruption strands. Cyst-like nerve clusters are located in the corners that are sensitive to damage and also are part in broadcasting the Marker signal. If shot at, they will summon Enhanced Feeders to defend the stomach, quite similary to white cells in a human body.
The Nexus speciment fought against can shoot many red pustule projectiles that explode upon contact and swing their massive claw-like appendages down on the player. When the pustules aren't disturbed, Feeders can burst from them and attack. The player must first target a large sac on its stomach, then destroy two of the yellow pustules on its mouth while the Nexus attempts to swallow the player. This must be repeated twice before the second fight sequence.
After shooting all of the yellow sacks, the specimen attempts to swallow Isaac and Carver a third time and they are slowly pulled into its stomach. They are plunged into an organ filled with an acid substance. After being attacked by three Nests, the Nexus spits them out. After several seconds of a frenzy, the Nexus collapses, dead.
- No direct death can happen in the Nexus specimen's chest caused by the creature, but Isaac or Carver will die from the Enhanced Feeders as they do normally outside if their health reaches critical levels.
- If Isaac or Carver fails to shoot the yellow spots on its mandibles while it is sucking them in, it will suck them in and chew them up before spitting them back out. They will die if their health was low.
- If they happen to be under the Nexus' blade when it smashes it on the ground, they proceed to get ripped into pieces if their health is low.
- If Isaac or Carver run out of oxygen while in the creature's stomatch, they will simply drown. They can also be killed by the projectiles shot by the three Nests.
- It is best to use rapid fire weapons for targeting the chest cavity's sac as well as the nests inside the stomach.
- As it pulls Isaac or Carver in, fire at the mouth's pustules. The pustules turn red as more damage is inflicted.
- Be sure to have a close quarters combat weapon (like a hydraulic hammer) when inside the Nexus. Flee to the cage when the fighting gets too rough after targeting the nerves.
- If you are using a rapid fire weapon, it is usually advisable to ignore the pustules that the beast spits out, and concentrate on the chest cavity. Once you deal sufficient damage, the creature will attempt to suck Isaac or Carver into its mouth, and all spawned Feeders will be consumed in the process.
- The specimen where Isaac and Carver must venture into was named by the SCAF research team as "Nexus-001", with the number indicating that there were more than one Nexus as suggested by the other warehouse being ripped apart as well as three others seen frozen solid at the base of the hill where the Alien Machine is located.
- The Nexus looks like a praying mantis (Explained when the tentacles fold during an attack) during the fight, but a look at the body suggests a centipede. This may be because the developers wanted to base it on insects, but thought it would be better to combine them in an unrecognizable way.
- The Nexus possesses eyes and has a digestive system, which is strange considering that most Necromorphs are only composed of dead tissues and have no need for organs.
- The Nests in its digestive tract may be a secondary line of defense to kill anyone that the Nexus has eaten but not killed yet.
- Another possible theory is that since Tau Volantis was once an entirely aquatic planet, this life form is in fact a Necromorph version of a large sea creature.
- When the Nexus is killed, the player receives an achievement/trophy (if playing on the PS3 or Xbox 360) which states that the Nexus is a Hive Mind, which might mean that the Nexi are specific types of Hive Minds or that they are the same as the Aegis VII variant but the only difference is that they were made from the extinct alien species, not humans like the Hive Mind.
- In Chapter 11, several enormous creatures can be seen frozen in the ice shortly before the appearance of The Nexus. They all bear extremely close resemblances to The Nexus, hinting that there was or still are more than one on Tau Volantis.
- The design of its head strongly suggests the Nexus may in fact be a Necromorph variant of the ancient Alien species that existed on Tau Volantis before the arrival of humans. It is a variant of a hive mind, that was created from Alien biomatter as opposed to Human biomatter, which was the main component of the Hive Mind on Aegis VII.
- The head of the Nexus bears some resemblance to the Xenomorph Queen from the 1986 movie Aliens, this can best be seen in the concept art for the Nexus.
- Sometimes during the battle, unknown tentacles or body parts flap up and down. It's unknown why The Nexus does this. Players sometimes jokingly refer that it's thinking: HEY! NEW FOOD! or out of anger (most possibly because Isaac and Carver are hurting it by shooting its weak spots).
- It is possible that the Moon had telepathically ordered the Nexus creatures to stop the Machine from activating as the three Necromorphs are seen at the base of the frozen mountain that has the Machine hidden inside it, frozen in a position that looked like they were preparing to climb up the mountain or tear it down. However, they were too late as the remaining alien survivors managed to activate the Machine, freezing everything in place, same as the three Nexus.