Legion, also known as David Haller, was created by writer Chris Claremont and artist Bill Sienkiewicz and first appeared in New Mutants #25, marking his introduction into the Marvel Comics universe.
Legion received his first ongoing solo comic book series, exploring his complex personality and multiple personalities, expanding his character depth.
Legion was reintroduced prominently as a complex and pivotal character in the 'X-Men: Legacy' series, gaining renewed popularity.
Legion made his live-action debut portrayed by Dan Stevens in the critically acclaimed FX television series 'Legion', bringing the character to a broader audience.