Sailor Pluto is introduced as a very mysterious, enigmatic woman, slightly older than the other Sailor Scouts. She is distant and cold to almost everyone except for Chibiusa, who she acts as a guardian for. She reveals a human form, Setsuna, and pursues a life as a human being, studying physics in university.
Pluto's main task is guarding the Portals of Space and Time. She displays an almost omniscience, which is explained as being able to watch through the gates of time. In the anime, she is considered one of the guardian Senshi, along with Sailor Neptune and Sailor Uranus, and like them, she wields a special weapon of her own, the Garnet Rod. The rod is topped by the Garnet Orb, which is used mostly in her attacks later in the series.
Pluto is a solitary figure who is given three taboos that she must not break by Queen Serenity: She must not travel through time, she must not abandon her post at the gate and she must not stop time. If at any point she disobeys those orders, her life becomes forfeit. Throughout the anime and manga, she breaks all three rules and dies accordingly. She is reborn each time.
Like all of the Senshi, Pluto is gifted with abilities much beyond normal humans. Using the phrase "Pluto Power Make-Up," she is able to transform from Setsuna Menoh to Sailor Pluto.
Pluto's attacks regularly reflect her attachment to death and the underworld as a reference to the Roman God, Pluto. She whispers her attack "Dead Scream," unlike all other Senshi who generally scream their attacks. The attack is channeled through her staff and in a manner similar to the other Guardian Senshi, is shot out in the shape of a ringed planet towards the enemy. Pluto later develops the "Cronos Typhoon" which is a wave of energy that slams into the target with devastating results.
Since Pluto is the guardian of space and time, she has access to abilities to alter both. While it is taboo to do so, she has been shown turning back time and traveling through it to save the world and the other Senshi from mortal danger.