Nebuchadnezzar's Key (ネブカドネザルの鍵, Nebukadonezaru no Kagi) is an item smuggled out of Bethany Base by Ryoji Kaji during the attempted escape of the Third Angel. The key resembles a miniature human nervous system with the neck attached to the stylized key-like device. "Nebuchadnezzar" is written on the shaft of the key in cuneiform . The portable safe-box containing the key bears other writing in mysterious characters that resemble a simplified version of the symbols on the Angel-sealing hex pillars.
Kaji delivers the item to Gendo Ikari, upon which the following interchange ensues:
- Kaji: Now, as I promised... The stored Lost Number, kept as a backup. The guidepost towards the unification of all souls unto God.
- Gendo: Yes, used to open the door to Human Instrumentality... Nebuchadnezzar's Key.
The true nature of Nebuchadnezzar's Key remains unknown. Most fan speculation contends that, given the fact that the Key replaces the role of Adam's embryo in the original series, it is simply Rebuild's equivalent of a reduced Adam. It should be noted, however, that an entity equivalent to Adam in Rebuild has not been confirmed.
In Evangelion: 3.0 You Can (Not) Redo, the Key itself is not shown, but its case can be seen multiple times. The first time it is seen is when Fuyutsuki informs Gendo about Kaworu showing Shinji the result of the Near Third Impact, the second time is when Gendo is watching Lilith's severed head.
- Nebuchadnezzar was the the name of several Kings, one of whom invaded Jerusalem and exiled the Jews.