A.L.I.E. was a recurring character in the second, third, and fourth seasons. She was portrayed by cast member Erica Cerra and debuted in Blood Must Have Blood (Part 2). A.L.I.E. is a sentient artificial intelligence whose primary objective is to make life better for mankind. Its holographic avatar was modeled after Becca, its creator. It was responsible for the Nuclear Apocalypse and overseen the City of Light and served as a major antagonist in Season Three. In Perverse Instantiation (Part 2), Clarke managed to activate the kill switch, destroying A.L.I.E. once and for all.