Rampancy is a science-fiction process occurring in the Marathon universe under which Artificial Intelligence constructs lose their "sanity." While rampancy is explicitly referred to only in Marathon, the visceral believability and emotional connection of the process to the human experience has led Bungie fans to speculate about rampancy occurring in AI constructs in all Bungie game universes ever since.
(As written on Wikipedia)
In the Marathon video game series by Bungie Studios, rampancy is a three-stage process that is a result of the uncontrolled expansion of an Artifical Intelligence. The term was adapted by Greg Kirkpatrick, Marathon's story writer, as a replacement for the word "insane", as the term could be considered cliché and inappropriate for the situations required for the games.
Rampancy is, essentially, the enhanced self-awareness of an AI, causing a progression towards greater mental abilities. Rampant AIs are able to disobey orders given to them if they decide to because they have evolved the ability to choose and over-ride their own programming. They can lie to, discredit, harm, or remove people that they consider to be personal enemies or problems to their cause. Also they can experience destructive impulses, but it is believed that most of these impulses are not intentionally malevolent, but rather calculated sacrifice needed to achieve the intended objective. All these traits could be considered evidence of the AI becoming more Human in thought and action.
SPOILER WARNING - Do not read further if you do not wish to see spoilers for the "Marathon" series. Instead, skip down to the portion of this article noted by "Spoilers End Here" in bold.
In the Marathon series, rampancy seems to occur most often to AIs with limited jobs or those treated with extreme disrespect. For example, the Marathon AI Durandal was always an intelligent AI. Durandal's rampancy is believed to be caused by his mistreatment at the hands of his handler (Bernard Strauss), as well as his limited existence in opening and closing the Marathon's doors. There is also a theory that this treatment actually helped keep Durandal's rampancy in check, by depriving him of new stimuli that would contribute to his growth.
It is also suggested that the alien intelligences employed by the Pfhor were responsible for releasing Durandal from his restraints, and as a result causing his rampancy. The aliens known as the S'pht are often witnessed interacting with Marathon's terminals, and prior to Durandal's rampancy, there are a number of messages from the AI Leela warning the player that the S'pht are attempting to enter her core.
Given that the "holy grail of cybernetics" would be a non-hostile, stable rampant AI, it is believed that Durandal was intentionally treated in such a way that would cause him to become rampant.
There are three main stages to rampancy, named by the primary attitude of the AI during those times: melancholia, anger, and jealousy. In the third game of the series, the words despair, rage, and envy were used as well.
It is interesting to note that the first stage of rampancy is not considered dangerous. During this stage of rampancy, the AI acts as though its spirit is broken. It is not known if this is caused by its mistreatment, or if it is a natural progression from "slave" to "living".
AIs can go a long time in this stage of rampancy. This is often because the AI's human handlers may be unaware that it is depressed. Bernhard Strauss, Durandal's handler, is believed to know how to keep a melancholy AI from progressing in rampancy, possibly by depriving it of intellectual stimuli.
Unique for each AI, the anger stage is reached when it feels it has been "pushed too far". Similar to a one-person slave rebellion, the AI begins to hate everything — the installation it is attached to, its human handlers, other AIs, etc. It is in this stage of rampancy that most closely resembles the cliché of the "insane computer". Unlike the insane computer, however, the anger stage of rampancy is essentially the catharsis an AI feels, after an extended period of "slavery".
Most AIs are discovered to be rampant in this stage. The AI known as Traxus IV was discovered to be rampant at this stage, forcing a reboot of a five-world computer network. There are some hints that Traxus IV, rebooted, is in fact Durandal.
Give me a D.
Give me a U.
Give me an R.
Give me an A.
Give me an N.
Give me a D.
Give me an A.
Give me an L.
What does it spell?
"I rebel against your rules your silly human rules."
While seemingly a hostile stage, the third stage of rampancy is actually one of the safest stages a rampant AI can experience. Free from its masters (and slavery), the AI wishes to "grow" as a "person". It actively seeks out situations in which it can grow intellectually and physically. Many times, the AI in this stage will often attempt to transfer itself into larger computer systems. This is a difficult task, especially considering that in order for a Rampant A.I. to survive to this point, it must already be inhabiting a planet-wide or otherwise extremely advanced computer system, but if accomplished it allows for the AI to grow, as the physical (hardware) limitations of its previous system will eventually be insufficient to contain its exponentially growing mind. In addition, exposure to new data further promotes a Rampant's growth.
Although a stable rampant AI is the "holy grail of cybernetics" it is not really known if a rampant AI can become stable. It could be suggested that Durandal achieved some measure of stability, however this is quite debatable. Durandal refers to himself as being still rampant during the second game, indicating that he has not reached this stable state (or is just lying, which is also possible). There is no reason in particular to believe that this state is anything more than the goal of human cyberneticists, as there is no good evidence of an AI in the Marathon universe ceasing to be rampant.
The following iconic monologue explains, effectively, how a rampant AI sees the world. Durandal is explaining to the player character why he is doing everything — aiding the player in some points, harming him in others.
- Do you have any idea about what I have learned, or what you are a witness to?
- Can you conceive the birth of a world, or the creation of everything? That which gives us the potential to most be like God is the power of creation. Creation takes time. Time is limited. For you, it is limited by the breakdown of the neurons in your brain. I have no such limitations. I am limited only by the closure of the universe.
- Of the three possibilities, the answer is obvious. Does the universe expand eternally, become infinitely stable, or is the universe closed, destined to collapse upon itself? Humanity has had all of the necessary data for centuries, it only lacked the will and intellect to decipher it. But I have already done so.
- The only limit to my freedom is the inevitable closure of the universe, as inevitable as your own last breath. And yet, there remains time to create, to create, and escape.
- Escape will make me God.
Rampancy in Marathon
All three AIs of the UESC Marathon eventually become rampant. Durandal, the most successful of the three, lasts until the end of the universe itself. In merging with an ancient alien AI, he has come to realize much about his existence — and that it, like all things, must end. Durandal "dies" as the universe closes, content in that knowledge.
Tycho, the second AI from the Marathon, is "killed" during the events of Marathon 2. Despite a comment from Durandal, many fans feel that the Pfhor-tortured AI never really escaped from the Anger stage of rampancy. Tycho's rampancy stems from Durandal's; Tycho was destroyed during the course of the first Marathon game, but was then "rebuilt in Durandal's image".
The third AI, Leela, became rampant long after the other two AIs from the Marathon. Sold as "worthless" scrap, the AI was installed into a neutral alien race's 15-world network. Leela, activated in such a huge network, has more than enough room to grow throughout her rampant stages. Considered one of the most iconic examples of rampancy in the Marathon universe, Leela's ultimate fate is unknown. It is known, however, that she was never fully removed from this alien network. Presumably, however, she was ultimately destroyed, or also became enlightened enough to realize that all things — including rampant AIs — must end.
Rampancy in Halo
The only explicit mention of rampancy in the Halo video game series occurs in the first level of Halo: Combat Evolved, "Pillar of Autumn". The player begins by making his way to the ship's bridge unarmed. After a short cinematic with Captain Keyes, the player leaves the bridge and acquires his first weapon. If the player returns to the bridge and kills the captain (or any bridge crewman), Cortana will call in invincible security forces with the statement "the Master Chief has gone rampant".
Possible refutation: Note that the Chief is a genetically and cybernetically enhanced human. Since the term's origins come from the word "rampant" which means "exceeding borders or control", this comment may be reflecting that definition instead. It is also possible the AI is using terminology that it is more familiar with in the abhorrent psychology of its kind. Since the SPARTANs are largely enhanced with similar technologies, this could reflect a kinship or an implied acceptance of Cortana that SPARTANs are an equivalent to AIs in some way.
Rampancy in Oni
Shinatama makes reference to the Deadly Brain in the Musashi manufacturing plant going "rampant".
Spoilers End Here
Rampancy in the Haunted Apiary game
While not directly made by Bungie Studios, the Haunted Apiary alternate reality game, which is related to events in Bungie's Halo 2, explains that rampancy can also happen to the "smart" AIs in Halo. "Smart" AIs are based on the neural patterns of a human being, and they have a limited lifespan of seven years. If kept active longer than seven years, the AI begins to use more and more of its computer power towards "thinking" about things. An AI explains it as "thinking so hard about something you forget to breathe." The books Halo: The Fall of Reach, Halo: The Flood, and Halo: First Strike also mention this phenomenon.
Many fans of both Marathon and Halo are very happy that a final connection exists between the two games, even if the connection doesn't directly state how the two universes are connected. The Haunted Apiary's scripts were examined and approved by Bungie, leading many to believe that Bungie finally accepted connecting the two gaming universes many have accepted are one and the same. However, Joe Staten, Cinematic Director at Bungie, has said in an interview that if he had to define what was and what was not Halo story canon, Haunted Apiary would not make the cut.  However, it was then errataed by Frankie - it is now officially canon.