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 the Mass Production Evas together with Shinji Ikari and Unit-01 started resonating. 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. This was the plan laid forward by SEELE who had for some time plotted an artificial evolution for mankind.
At the same time, Rei Ayanami (who is in reality Lilith) felt Shinji's pain, and rushed to his side after having regained her original form - that of Lilith. Rei Ayanami is able to intervene in the Instrumentality process, ensuring that Shinji is conscious enough to undo the process. Rei Ayanami appeared before Shinji, questioning him about what he truly wanted in life. Central to the story's themes of anti-escapism, Rei warns Shinji about the world he's creating for himself, egging him to live in real 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 across 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.