The "Slayer line" refers to a specific lineage of characters in the Buffy the Vampire Slayer universe, particularly focusing on the chosen individuals known as Slayers. These Slayers are young women who possess enhanced abilities and are destined to battle supernatural forces, primarily vampires. The line is activated when a Slayer dies, allowing another girl to inherit the powers. The concept of the Slayer line is central to the series, as it explores themes of destiny, sacrifice, and empowerment. Each Slayer has unique experiences and challenges, contributing to the ongoing struggle against evil. The line's history is rich, with notable Slayers like Buffy Summers and Faith Lehane shaping its legacy.