Model: Production Type
Developer: NERV-02 (America)
Evangelion Unit-04, also commonly referred to as Eva-04, is never actually shown in neither the series nor the movies. It is one of two Evangelion Units constructed in American, or more specifically by NERV-02 (the second branch) in Nevada.
The unit was subject to an experiment attempting to integrate a prototype Sē Engine constructed based on data salvaged from Shamshel, the Fourth Angel. Although details are scarce, the experiment was deemed a failure once the entire Nevada site (along with every facility in a 89km radius) vanished during what was believed to be the final installation of the device.
Ritsuko Akagi theorized that the area was consumed by a Dirac Sea, similar to the one that comprised Leliel, the Twelfth Angel. The direct cause of the failure and subsequent catastrophe however remains unknown.
The incident had caused much fear in America, resulting in the immediate transfer of it's sister-unit (Evangelion Unit-03) to NERV Headquarters in Japan. This fear-driven haste also caused the pilots transporting Evangelion Unit-03 to take a questionable flight path through an area where Bardiel, the Thirteenth Angel, had spawned. The result was an infected Evangelion Unit-03 that had gone renegade the moment it was activated.