Conversation so far:
what was the fictional character Legion?
Legion is a fictional character appearing in American comic books. Legion takes the role of an antihero who has a severe mental illness including a form of dissociative identity disorder.
who did Legion have an affair with?
Legion did not have an affair.
was Legion married at the time?
Legion never married.
where did Legion come from?
Legion is the mutant son of Professor Charles Xavier and Gabrielle Haller.
what was wrong with Legion?
Legion has been described as having multiple personality disorder.

Question: when did he become legion?
Self-contained rewrite: when did Legion become legion?