What part of batman does the joker come in to?

The Joker is one of Batman's most iconic and enduring adversaries in the DC Comics universe. He serves as a chaotic foil to Batman's quest for justice, embodying anarchy and unpredictability. Their dynamic explores themes of morality, sanity, and the nature of good versus evil. The Joker's presence often challenges Batman's principles and forces him to confront the darker aspects of his own character.