Berserk
Berserk (暴走, bousou) is a state an Evangelion can enter in which she has gone beyond Nerv's ability to control, characterized by a battle-frenzy in which the Eva's strength and capabilities drastically increase. Those Evangelions with jaws bolted shut with force them open and bellow wildly during berserker mode, and show savage, animalistic tendencies in their movement and behavior.
"Berserker mode" operates in defiance of the current level of human scientific knowledge, and Dr. Ritsuko Akagi is aghast when Eva-01 goes berserk in Episode 16 with its internal batteries completely drained. In Episode 20 it is revealed that no known power source could be detected during the incidents (the second in Episode 19) when the batteries were drained.
During these incidents, the Eva's resident soul appears to bypass restraint mechanisms and wield her own body, although it's arguable how much "conscious control" the soul has over the Eva's actions. (The discrepancy between the behavior of Yui Ikari — prior to her "death" — and her Evangelion incarnation is often cited to this effect.)
Nerv is very aware of the danger an out-of-control Evangelion poses and is extremely concerned about keeping the Evas bound and restrained at all times. No attempts at artificially initiating a true berserker mode have ever been made, although the use of the Dummy Plug in Episode 18 results in a seemingly similar state of greatly increased strength and savagery. Several incidents of increased strength, savagery, or battle rage have been displayed by Evangelions, in addition to the "true", unpowered berserker mode.
Berserker behavior by individual Evangelions
The Series
Evangelion Unit-00
Eva-00 has two incidents (in Episode 05 and Episode 14), both occurring when a pilot attempts to synchronize with her. During her activation test with Rei Ayanami, the Entry Plug is auto-ejected (apparently by the Eva herself) and Eva-00 continues to move undeterred until her power runs out. The second incident, involving Shinji Ikari, is extremely similar, except the Eva rejects the auto-eject signal. In both cases, the Eva shut down after she ran out of internal power, and did not restart, falling short of going "truly" berserk.
Evangelion Unit-01
Eva-01 is the most notorious berserker. Her abilities to move both independently and without power are effectively established before her initial activation, when she moves her arm to shield Shinji from falling lights (in spite of being loaded with a Signal Termination Plug). Not long after, she goes out of control during her first sortie, against Sachiel, exhibiting a bestial and uncompromising "battle rage" that doesn't stop until the Angel is down. Similar behavior occurs when Eva-01 brings about Leliel's gruesome destruction, and, later, mauls and devours Zeruel, although, unlike the incident with Sachiel, these both occur when her umbilical cable is disconnected and internal batteries fully drained, thus classifying as "true" berserker mode. Shinji is not involved in any of the berserk incidents, being blacked out in the first two and dissolving into LCL in the third.
In Episode 25', Eva-01 moves independently once more, setting off a crucifix-shaped explosion and growing "wings of light". From this point forward, Eva-01 seems to be in complete control of herself.
When controlled by the dummy system in Episode 18, Eva-01's behavior is indistinguishable from her true "berserker mode".
Evangelion Unit-02
Eva-02 sets off a crucifix-shaped explosion and goes into a battle rage in Episode 25', performing incredible acrobatic feats and casting an offensive A.T. Field against attacking JSSDF units. After losing all battery power (the umbilical cable was destroyed by the JSSDF) and being ravaged by the Mass Production Evas, the Eva goes berserk and moves without any power supply, moments before its destruction.
Eva-02's berserk is different from those exhibited by Eva-01 and Eva-00 previously because the pilot, Asuka, appears to be in primary control of the Eva throughout. She may have willed the Eva into moving without power, having fully understood that the soul of her mother, Kyoko is inside. However, certain details, such as the fact that the Eva vocalizes during the JSSDF battle and while moving without power, also suggest that Eva-02's final sortie is a "joint effort" if anything, although this is heavily disputed.
Evangelion Unit-03
Eva-03 was infected by the Angel Bardiel during activation and initially behaved very much like Eva-01 in her first berserk incident, breaking open its jaws and bellowing, although this appears to have been the work of the Angel itself and not the resident soul. Despite being heavily mutated by the Angel, Eva-03 was ripped apart by a Dummy Plug controlled Eva-01, so the Angel appears to have been unable to harness the Eva's latent power and strength.
Rebuild
Evangelion Unit-01
Evangelion 2.0 shows Eva-01 entering a berserk-like state against Zeruel, signified by its eyes and neon green trim turning red. In this state, the Eva demonstrates several Angelic abilities including an extremely devastating energy attack from its eyes, reforming her severed arm from her AT-field then further morphing it into geometric shapes (not unlike Ramiel's transformations from) before releasing a powerful shockwave and at the top of her power, manifesting a halo. Unlike in the series, Eva-01 doesn't devour Zeruel but rather establishes contact between Shinji and the Angel, allowing him to extract the soul of Rei Ayanami from the Angel's core before the Eva ruptures it and absorbs the fluid the Angel has turned into. After absorbing the Tenth Angel, Eva-01 receives a massive increase in power and turns into a glowing energy being, almost setting off Third Impact before she's impaled by the Mark.06's weapon which finally deactivates her.
This incident is distinctive in that the Eva is depicted as under the pilot's control for most of its duration, despite having many characteristics of a berserk incident. When Misato asked Ritsuko if Eva-01 has gone berserk, Ritsuko as unable to provide an answer. Whether or not Yui played some role in the events is disputed and remains to be seen.
Evangelion Unit-02
The Beast Mode activated by Mari in Eva 2.0 resembles a berserk in many ways, but does not qualify since the Eva is not actually out of control.
Notes
- Bousou literally means "out of control". "Berserk(er)", however, is the official English rendition, as indicated by the document Shiro Tokita displays in Episode 07.
