Berserk Evangelions are characterized by a savage, animalistic battle frenzy in which their strength and capabilities drastically increase. Units with jaws bolted shut typically force them open and bellow wildly while berserk.
"Berserker mode" operates in defiance of the current level of human scientific knowledge. Dr. Ritsuko Akagi is aghast when Evangelion Unit-01 first moves without power or pilot input. and later goes berserk against Leliel and Zeruel with internal batteries fully drained. It is revealed that no known power source could be detected during these incidents, but no understanding is gained of what actually was powering Eva-01 at these times. However, it can be deduced that there must be an upper limit to "berserk-fueled" independent movement, otherwise consuming Zeruel's S² Engine would not have been necessary.
During these incidents, the Eva's resident soul appears to bypass restraint mechanisms and act on its own. Some have argued against this, citing the discrepancy between the known behavior of Yui Ikari prior to her "death" and the savagery of her Evangelion incarnation. This could, however, be attributed to several factors, such as the fact that she is a mother protecting her child. Since the Evas are empty vessels before having souls salvaged into them, and these souls are the source of the Evas' "will" and "heart", it is ambiguous what could be directing the berserk Eva if not its resident soul.
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. Several incidents of increased strength, savagery, or battle rage have been displayed by Evangelions, in addition to the unpowered berserker mode.
Save for Mari Makinami Illustrious inciting Eva-05 into a semi-berserk state, no known attempt has been made to artificially or intentionally initiate berserker mode. Instead, technological advances strive to achieve a similar level of power under controlled circumstances. The Dummy System, along with the Beast Mode of Rebuild, result in similar states of increased strength and savagery, but as the resident soul is not in command, these do not constitute actual berserk incidents.
Berserker behavior by individual Evangelions
Eva-00 has two incidents (in Episode 05 and Episode 14), both occurring when a pilot attempts to synchronize with it. During the activation test with Rei Ayanami, the Entry Plug is auto-ejected (apparently by the Eva itself) and Eva-00 continues to move undeterred until its power runs out. The second incident, involving Shinji Ikari, is extremely similar, except the Eva rejects the auto-eject signal. Unlike the Eva-01 incidents, in both of these cases the Eva shut down after it ran out of internal power, and did not restart using whatever power moved Eva-01 during its berserk incidents.
Eva-01 is the most notorious berserker. Its abilities to move both independently and without power are effectively established before its initial activation, when it moves its arm to shield Shinji from falling lights (in spite of being loaded with a Signal Termination Plug). Not long after, it goes out of control during its 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 the umbilical cable is disconnected and internal batteries fully drained. 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 completely under Yui's control.
When controlled by the dummy system in Episode 18, Eva-01's behavior is very similar to berserker mode, but as its actions were directed by the Dummy System itself, not the resident soul, this is not a genuine berserk incident.
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 briefly moves without any power supply before its destruction.
Eva-02's berserk is different from those previously exhibited by Eva-01 and Eva-00 because the pilot, Asuka, appears to be in primary control of the Eva throughout. However, the fact that the Eva vocalizes during the JSSDF battle and while moving without power (both in and out of synch with Asuka) -- which up until this point has occurred only when the berserk Eva's soul has taken command -- suggests that Kyoko's soul was actively involved on some level. This would also explain how Asuka could access many of Eva-02's higher powers.
Eva-03 was infected by the Angel Bardiel during activation and initially behaved very much like Eva-01 in its 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.
Evangelion 1.0 has Eva-01 go berserk in the battle with Sachiel, identical to the incident in the original series, although the incident with the falling lights does not occur in 1.0. Unlike the TV series, both Misato and Ritsuko seem to know of the berserk state.
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 its severed arm from its A.T. Field then further morphing it into geometric shapes (not unlike Ramiel's transformations from) before releasing a powerful shockwave and at the top of its 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 being impaled and deactivated by the Mark.06's weapon.
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 is unable to provide an answer. Whether or not Yui played some role in the events is disputed and not yet clear.
For more information, see Eva Pseudo-Evolution.
During battle with the Third Angel, Mari Makinami Illustrious becomes unable to properly synchronize with Eva-05's prosthetic limbs, and is forced to yield control of one to the Eva itself. Entering a semi-berserk state, Eva-05 opens its jaws and helps destroy the Angel's core, self-destructing moments later.
Notes & References
- 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.
- Neon Genesis Evangelion. Episode 01.
- Neon Genesis Evangelion. Episode 16.
- Neon Genesis Evangelion. Episode 19.
- Neon Genesis Evangelion. Episode 20.
- Neon Genesis Evangelion. Episode 22.
- According to the Eva 2.22 script, the Eva is said to be in 半暴走状態, han-bousou joutai ("semi-berserk state").