The Evil Within Wiki

The STEM system is the brainchild of the genius scientist Ruben Victoriano, and an instrument for MOBIUS to achieve their goal of total world dominion.


Ruvik created STEM with the intention of using it to create a reality of his own design so that he could be with his sister Laura Victoriano.

Dr. Marcelo Jimenez, being a long time friend of Ruvik, decided to help Ruvik out and provide him with materials and patients. Around this time, MOBIUS had made Jimenez a member and had him share his work with them. After Jimenez published Ruvik's work, MOBIUS became interested in it and wanted to be involved. Mobius ended up putting Ruvik in a tight situation; either he finished the project, or they would remove him from the equation. The relationship between MOBIUS and Ruvik only became worse and worse over time.

At first, STEM was such that it necessitated that subjects be plugged into the system via cord, and anyone could be hooked up to the machine. The next iteration was instead wireless, and an even later version allowed Ruvik to modify it so that only he who could operate it. Brain synchronization was the only way to access STEM. In an attempt to get around this, MOBIUS made efforts to find someone who had similar brain waves as Ruvik; this was where Leslie came in, for his ability to brain sync was identical to Ruvik. This sync was derived from experiencing specific trauma: Ruvik had lost his sister and murdered his parents, while Leslie had lost his whole family.

After this, The Administrator demanded that Ruvik fix the changes he had put in place so that capturing/using the unstable Leslie would not be necessary. When Ruvik refused, they had no other choice but to take what they needed from him and do it themselves. They killed Ruvik and took his brain, which they then placed within the center of the STEM system to act as a core, attempting to then resume testing. However, Ruvik's lingering consciousness was slowly taking over STEM. He had turned the majority of the STEM system itself into a hellish landscape of various levels, with each subject who was attached to it having some subconscious dream-like influence, but only Ruvik was in total control of his influence. He then began to kill anyone who was sent into STEM.

Once MOBIUS realized this they had his brain removed from the core. Though they thought they had gotten rid of him, they soon learned that Ruvik's consciousness was still present within STEM - its state as a hellscape persisted. Jimenez and The Administrator together devised a plan: they would send a group of people into STEM - the more "sane" individuals amongst those sent in would be used to cleanse the system and to neutralize Ruvik. They planned to send Juli Kidman in, who was already undercover as a Junior Detective, to complete this task. They also planned to send her with her two colleagues Sebastian Castellanos and Joseph Oda. They saw Sebastian as a threat due to him getting closer to the truth and finding out about them, and sent Joseph to ensure that they left no loose ends.

Jimenez wanted to prove himself useful by defying his orders and attempting to complete the task himself - desperately he craved to make Mobius see his worth, letting him potentially rise higher in their ranks. He activated the wireless STEM switch himself when the police, including the detectives arrived at Beacon Mental Hospital. This is where the game began. Turning on the wireless machine caused everyone in the area to be dragged into STEM. However, the effect was slow in fully taking effect. Seizing the opportunity, Ruvik used the small period where reality and the mindscape blurred: he manifested in the hospital and killed the entire police squad before wounding Jimenez. Within STEM already (though obviously failing to realise this), the detectives found the doctor and desperately attempted to escape from the hospital in an ambulance. It was too late, however, as STEM had overcome the delay and had fully taken effect, dragging everyone into the mindscape beyond. They were all trapped inside of STEM.

(In the DLC, it shows the sinister application of the system in controlling human's subconsciousness through a high-pitched frequency emitting from the system.)



The STEM system as it appeared in the series is composed of several bathtub-like ports called Terminus. A would-be STEM occupant will then be seated in one such port, whereupon an electrically-induced coma will knock them out and create a mental projection in their image within the connected world.

While the earlier iterations of STEM utilize physical jacks plugged into a person's cranium to inject them into its worlds, more advanced versions of the device rely on wireless signals instead, which eliminates the need for a physical Terminus and can potentially work on a global scale.


All Terminus ports are then connected to a central Core processor. This Core in itself is a biologically-living component, being comprised of a whole person or their brain, whose mental patterns are then used as a map to project a virtual world in which other plugged-in subjects can inhabit.

While MOBIUS' initial Beacon prototype has an exposed Core (essentially Ruvik's brain in a jar), their later revision to the system has a dedicated Core chamber complete with locks and a security terminal.


Connecting to STEM can be achieved wirelessly via specific frequencies emitted from a source, which deposits the subject into the simulated world immediately without them knowing it. Another, less speedy method is to sit in a STEM pod and be connected via an electrically-induced coma, which gives the pod occupant the sensation of them being pulled down into a large water body, where they will appear to fall before suddenly halting due to synchronization. In its earliest days, an individual must be connected physically into STEM space with a dedicated jack (see above).

Both methods have their pros and cons, as while Ruvik's version of STEM can create instant connections over a wide area without the need for pods, the configuration is limited to simulating an individual's immediate surroundings before slowly bending it to the creator's will. The newer device tested by MOBIUS, while slower and a lot less comfortable jacking into, can deposit the pod occupant into any pre-programmed backdrop without hassle, thus allowing for controlled insertion and extraction if needed.


STEM is a system that allows multiple minds to be brought together and connected. Using a bathtub-like pod called a Terminus, subjects can be connected to one particular mind and experience the memories, and perceptions of the individual. There are two ways to connect the person to the system: through physical connection via plug and through wireless frequency (advanced version).

However, the applications of STEM are numerous. This includes curing people of their mental illnesses, interrogation of criminals and learning people's memories.

It seems that in order for the STEM system to work, it requires a main brain/mind or subject to act as a core. This would load his/her world as base, for the others to come. According to the Administrator, the core requires a mind to be innocent and pure to support multiple different kinds of personality. As the result, the core must be the mind of a child. However, based on the research of Yukiko Hoffman, the core must have an unfettered ego to interlink the different personalities of people connected to STEM as well as retaining their own personality. In her own words, there are two types of candidates that can serve as a core: a psychopath with egomaniac mind and a child. Due to the event that involves Ruvik in Beacon Hospital, MOBIUS has opted to choose a child rather than a psychopathic individual.

During the events of The Evil Within 2, it is stated in a report that if there are enough people being connected to STEM to serve as processing and memory components to generate 2 million exabytes (1 EB = 1,0246MB), the STEM system would be powerful enough to wirelessly connect to every human on the planet, enabling MOBIUS to control the world.

For MOBIUS members, all of them have a chip implant that connects them to STEM in the real world, even if they are not within the system mentally.

According to Dr. Hoffman, the mind of a psychopath is extremely dangerous to the STEM environment since they can have powerful manipulation over STEM, such as the case with Stefano Valentini.


Any given individual connected into STEM space are liable to become dominated by the system's psychological disruptions. This is a gradual process, the rate of which depends mostly on the psychological fortitude of a subject, meaning those who are weaker-willed (e.g. Joseph Oda) are more susceptible to domination than the mentally-hardened ones (e.g. Sebastian Castellanos). This resistance can also be conditioned via specialised training, which is included as part of the standard orientation procedure for MOBIUS personnel. Regardless, there is currently no true defense against psychological erosion from STEM usage, and individuals connected to it will eventually turn at some point, some earlier than others.

As they become more and more subsumed by the domination effects, a subject becomes more and more unstable, the earliest symptoms of which being memory losses or headaches. Their mentality then degrades exponentially over time, which the subject may or may not be aware of. At later stages, an individual may exhibit and repeat unusual behavior (e.g. Valerio Jimenez).

At the height of their domination, the subject either becomes a Haunted or a Lost, depending on the specific STEM space they are connected to, and a fully-dominated subject is irreversibly lost. Certain subjects with special psychological makeup can instead be transfigured into unique creatures like the Sadist or The Keeper, either spontaneously or at the discretion of the Core. These subjects, while not entirely feral, are ruthless, murderous and cannot be reasoned with.

Should a damaged mind be safely disconnected from STEM, the system would leave specific imprints within their psychological makeup that can cause permanent nerve scarring.

STEM Machine Rooms

The main area used to plug people directly and physically into STEM. It is usually a circular room consisting of bathtub-like pods where subjects are placed, and a central area containing the core.

The Beacon Prototype's STEM machine room made multiple appearances inside of STEM visited by both Sebastian Castellanos in the The Evil Within, and Juli Kidman in The Consequence. Multiple prototypes of the machine were also found in different places and they all differ in complexity.

Locations in STEM

Most of the areas in The Evil Within are locations in the real world as well as STEM. The real life ones are different and usually infested by Haunted, but all are based on the memories of people connected to STEM, usually the main characters. However, some are only seen in STEM and are usually created by someone inside as a completely altered version of a real world room.

In The Evil Within 2, the entire city of Union is constructed within STEM by MOBIUS and does not exist outside it. It is infested by Lost.


  • At present, it is unclear what the STEM abbreviation stands for, other than to aid in a wordplay based on "brainstem" to work with the prevalent brain imagery throughout the two games.
  • The STEM system seemingly has an undocumented function where the psychological profiles of an individual can presumably be logged and simulated at will independent of their actual connection to the system. In all likelihood, this is the most plausible explanation for Oscar Connelly's appearance in The Executioner despite his death prior to the events of the DLC and the survival of Joseph Oda, despite the demise of his STEM self.
  • It's unclear how many people STEM was able to pull in via the wireless signal at the start of the game, and it's unclear what happens to their bodies in the real world as well.
  • It is stated that it will require 2 millions exabyte to control the planet wirelessly and a single person in the STEM can generate 100 exabyte. Therefore, MOBIUS needs at least 20000 people to be connected to STEM to achieve their goal.
  • Even though Sebastian, Connely and Joseph were pulled into STEM via the wireless signal, they were placed by MOBIUS in the bathtub-like terminuses when they arrived at the scene and were plugged directly into the system, as shown in glimpses from Sebastian's point of view, as well as at the end of the game. Kidman, on the other hand, was pulled in via the wireless signal, but was not plugged into the system and instead, she seemingly woke up standing.
  • During The Consequence, where you play as Juli, after you see the cutscene where Leslie is running away from you, you can walk to the center of the STEM machine room where Ruvik´s brain is and shoot it. A fake ending will play and then things glitch back to Juli standing right where she was before. You will get an achievement for this.
  • In recorded experiments with Terminus ports in The Evil Within 2, it is stated that there are possible, undocumented sublevels of STEM that are inaccessible and inescapable by normal means; comparable to a form of limbo. Subjects in these tests are theorized to have been lost or died.
  • The master password to MOBIUS' STEM system is "stemadmin123", which can be observed in a split-second during the finale of The Evil Within 2.
  • According to The Art of The Evil Within, the STEM system was developed through the centuries as a means to rid patients of their insanity while also concealing a more devious purpose. It's name was given by those who have seen it, likening it to the stem of the brain.
    • Earlier variants of the STEM design had its occupants strung together while submerged in a large pool within Beacon Mental Hospital.