The Spear of Longinus (ロンギヌスの槍,“Ronginusu no Yari”) is an extraterrestrial artifact with the power to penetrate any A.T. Field and immobilize beings of god-like power.
Physically, the Spear of Longinus resembles a long, red bident on an Evangelion scale. Its structure is inherently double-helical (in its normal configuration), with the majority of its length being straight and composed of two strands which are tightly interwoven. At one end, the two strands unwind and form two massive tines.
While the bident is the Spear’s default shape, it also has metamorphic capabilities. When thrown at the Angel Arael, the tines wrap together to form a seamless piercing object. Upon encountering Arael’s A.T. Field, the “flaps” of the Spear open up, revealing white, gill-like structures that seem to aid the Spear with self-propulsion under conditions of extreme resistance. Finally, the Spear’s bident shape is perpetually altered by Unit-01 inEpisode 26’ when she separates the two helices, and the Spear takes on a form reminiscent of a horizontally elongated infinity symbol, ∞.
The Spear may be considered to be a weapon of “god-like” power. N² weapons have enough destructive potential to bring minor to moderate amounts of damage upon some of the weaker Angels; and Evas can usearmaments against Angels after nullifying the Angels’ A.T. Fields with their own. However, the Spear of Longinus is capable of piercing the active, unneutralized A.T. Field of any Angel or Evangelion, entirely by itself.
The Spear is not of Terran origin, having been created by the First Ancestral Race, an ancient extraterrestrial humanoid species. The one seen in the show is also not the only Spear of Longinus created: Every Seed of Life, including both Adam and Lilith, was sent with a counterpart Spear, meaning seven in all. At least one established function of the Spears is that of a “security device” capable of safeguarding the First Ancestral Race’s plans should they somehow be compromised.
Spears of Longinus are technically alive and are even said to have wills of their own. The Spear featured in Evangelion belonged to Adam, whereas Lilith’s is believed to have been lost or destroyed during First Impact.