Danielle Rousseau
The monster is established in "Lost" in the first episode, "Pilot". The producers' initial plan was for the monster to represent the id, in a manner similar to the "id monster" from the 1956 film "Forbidden Planet". This idea was changed by the end of season one, when the character Danielle Rousseau describes the monster as a "security system" that protects the island. This plan was continued into season five, when Rousseau's husband, Robert, describes the monster as a security system that guards the island's Temple. It was not until season six that it was established that the monster was also The Man in Black.