Her parents gave her up for Slayer training at a very early age. Kendra Young did not know her own surname as she studied under her Watcher, Sam Zabuto. She is called when Buffy Summers dies at the hands of The Master in 1997; though Xander manages to revive her, Buffy's death nevertheless activates a second Slayer, causing two to exist. Kendra is fully versed in the Slayer Handbook and fighting techniques. She owns a stake called Mr. Pointy. Her appearance is the first time the Watchers' Council has been shown to identify potential Slayers ("What's My Line, Part One").
In her first year as the Slayer, Zabuto sends Kendra to Sunnydale after signs indicate that a very dark power is about to rise there. Kendra sees Angel kissing Buffy with his vampire face, and assumes that she too is a vampire. Kendra imprisons Angel in a cage to kill him by sunrise and surprises Buffy as she wakes up from a night on Angel's bed. After a physical confrontation, they learn that they are both Slayers (at the time, Spike and Drusilla had hired an organization of assassins to kill Buffy; it was thus intended to be a surprise when both Buffy and the viewer discover she is not an assassin). Rupert Giles tells them that two Slayers existing at the same time is unprecedented.
Meanwhile, Angel is taken unconscious by Willy the Snitch and sold to Spike and Drusilla. Severely weakened by sunlight, he as Drusilla's sire is to be used to return her to health. The Scooby Gang arrive to free Angel, and Kendra returns to her home country with a keepsake from Buffy.
Kendra returns in 1998 when her Watcher informs her that Acathla will open its mouth and suck the world into hell. Zabuto gave Kendra a sword, which Kendra passes on to Buffy after surprising her as she patrols. Kendra helps the Scooby Gang protect Willow Rosenberg while she performs the Ritual of Restoration. Drusilla and her vampire lackeys arrive in the library to stop the attempt to restore Angel's soul and after a brief fight, Drusilla hypnotizes Kendra and slits her throat, killing her ("see Becoming, Part One"). Following Kendra's death, Faith is called as a Slayer in Boston.
Kendra possessed the normal powers that come with being a slayer. She had inhanced reflexes, agility, speed, strength, and was a formidable hand to hand combatant. She has stated that she is a master of hand to hand weapons as well. Also worth noting, is that Kendra was a strictly traditional slayer, taking orders from her watcher and never straying from them. Kendra was also considerably less powerful (or skilled) than the Slayer, Buffy. Her strict uprbringing, lack of real emotion, and "by the book" attitude may be the reason for this, as Buffy once stated that she's good, but doesn't have enough "passion" to ever really beat her.