The Joker is a serial killer and a super-villain, a dangerous madman who dresses like a clown and commits violent crimes. He is often recognized as Batman's greatest enemy, living in and terrorizing Gotham City, although he spends most of his time in Arkham Asylum. In addition to being a deadly and unpredictable physical combatant, he is a brilliant and ruthless criminal mastermind. His crimes require no motivation other than his sadistic desire to show people the meaninglessness of life through pain and death, and the narcissism to see the world remade in his own image. He is constantly adapting his personality and his psychosis to respond to the world around him, sometimes a harmless trickster and at others a brutal mass-murderer. Batman is his only worthy opponent, and although he has passed up multiple opportunities to murder the dark knight, he has no such problems with killing Robin or crippling Batgirl. Although his origins remain unclear and shrouded in mystery, it is also known that prior to the chemical accident that scarred his mind and body he was the small-time criminal Red Hood.