in which episode this character first appear?
In season two episode "One of Them"
Ben Linus
Ben makes his first appearance in the season two episode "One of Them", where he is caught in a trap set by Danielle Rousseau (Mira Furlan). 
who is the leader of the others in lost Benjamin Linus who is this aforementioned? A fictional character on the ABC television series "Lost" who is the artist who played this role? Michael Emerson describe the role this character played in the series? He began as the main antagonist during the second and third seasons, but in subsequent seasons, becomes a morally ambiguous ally to the main characters what happens prior to the crash? Two days before the crash of Oceanic Flight 815, he discovers he has a spinal tumor
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Ben Linus [SEP] Seasons two to four
Ben makes his first appearance in the season two episode "One of Them", where he is caught in a trap set by Danielle Rousseau (Mira Furlan). He pretends to be Henry Gale, a man from Minnesota who crashed on the island while traveling via hot air balloon. Rousseau turns him over to Sayid, who takes him to the , where he is held captive and interrogated. Ben is exposed as a fraud when the body of the real Henry Gale is found, but he is set free by Michael Dawson (Harold Perrineau), a crash survivor whose son has been kidnapped by the Others.