The Third Impact is an event mentioned in Neon Genesis Evangelion and finally occurring in The End of Evangelion where Human Instrumentality was almost achieved. It began when Rei Ayanami (also the vessel for Lilith's soul) transformed into the Angel form of Lilith, and used Unit-01 as a catalyst. Shinji Ikari was inside of the Eva, as the Mass Production Eva units appeared and formed a Tree of Sephiroth. Soon afterward, Evangelion Unit-01 became the Tree of Life. This event is a global Anti A.T. Field event which terminates A.T. Fields of all living beings on Earth.
The process of Instrumentality began, and Rei Ayanami and Kaworu Nagisa appeared before Shinji, questioning him about what he truly wanted in life. After a long period of reflection and internal struggle, Shinji finally decided that an individual life was superior to living a life as LCL, causing Unit-01 to emerge from Lilith's eye. As Lilith started to fall apart, Unit-01 decapitated her, leaving a streak of red blood on the moon. Unit-01 used the Lance of Longinus and destroyed the replica Lances, bringing the Third Impact to an end. In the aftermath the Earth is devastated and looks like post-Second Impact Antarctica which was barren of life. It is unknown if plant or animal life could come back or not because of the effects of the Anti A.T. Field altering the chemical elements of the soil. The Third Impact could also be considered an apocalypse as the biological forms of life are destroyed by the Anti A.T. Field.