Klaus Mikaelson first appears in the Season 2 finale episode "As I Lay Dying," which is the final episode of Season 2. In this episode, he is introduced as an Original vampire and is revealed to be behind much of the conflict that has been building throughout the season. He arrives in Mystic Falls seeking to break a curse placed on him by his mother Esther centuries ago. Klaus's introduction marks a major turning point in the series, as his arrival sets in motion many of the central conflicts of the following seasons. The character, portrayed by actor Joseph Morgan, quickly becomes one of the show's most prominent antagonists and later a complex anti-hero. His presence fundamentally changes the dynamics of the show, introducing the mythology of the Original vampires and their extended family. Klaus appears briefly in the Season 2 finale but becomes a major fixture of the series from Season 3 onward.