Berserk

Eva 01's mouth opening when it goes berserk

Eva 01's forcibly tearing open its wired-shut jaws

Berserk (暴走, bousou) is a state an Evangelion can enter into in which she has gone beyond Nerv's ability to control her, entering into a savage battle-frenzy in which the Eva's strength and ability levels drastically increase. Those Evangelions with jaws bolted shut with force them open and bellow wildly during berserker mode, and show other animalistic tendencies in their movement.

"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 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.

Eva-00 has two incidents (in Episode 05 and Episode 14), both occuring 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.

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 Termination Signal 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 internal batteries are fully drained. 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.

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 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 berserking mode is different from those exhibited by Eva-01 and Eva-00 previously because the pilot, Asuka appears to be in control of the Eva throughout, although she appears to have an attained an exceptionally high synch ratio with the resident soul of her mother Kyoko. (It is worth noting that Shinji reached an impossible 400 percent synch ratio in the battle against Zeruel, at which point Eva-01 went berserk)

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 latent power and strength of a truly berserk Eva.

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.
• When controlled by the Dummy Plug system in Episode 18, Eva-01's behavior is indistinguishable from her true "berserker mode".