Luna Inverse (Japanese: ルナ＝インバース Romaji: runa inbāsu) is the Knight of Ceifeed and the older sister of Lina Inverse. She is two years older than Lina. Her name is never mentioned in any novel or manga and only once in the the final episode of Slayers TRY. Lina always refers to her as "that girl from hometown".
As the Knight of Ceifeed, Luna wields an immense amount of holy power. She can cut a Dragon Slave in half, and once defeated a plasma dragon with a kitchen knife. During Slayers TRY, Luna was the dragon priestess Filia Ul Copt's first choice to save the world from the prophecy of destruction. According to Hajime Kanzaka, Luna is more or less equal in power to, if perhaps somewhat stronger than Xelloss. It is not made entirely clear whether or not Luna is more powerful than Lina. Although Lina is plainly terrified of her older sister, during TRY, Luna thought Lina was a better candidate for saving the world from the prophecy of destruction. Luna currently works part-time as a waitress in her hometown of Zephilia. Her father is an ex-mercenary and her mother is an ex-sorceress.
Lina Inverse: Luna and Lina's relationship is not the most affectionate, to say the least (although Lina surprisingly calls her onee-chan, with the suffix -chan usually denoting close friendship or affection). Apparently, when they were younger, Lina would misbehave and Luna would "punish" her. (The most notorious incident between the two was when Lina set up a device that projected an image of Luna while she was taking a bath and sold it to lecherous boys). These punishments are probably why Lina is so terrified of Luna. This is further noted in episode 13 of Slayers where Lina manages to suppress the pain of anti-magic circlet's electrical shock in order to cast a spell, noting "Compared to what my big sister used to put me through, that was a piece of cake!" Luna also has a surprising amount of control over Lina. During TRY, all it took was a simple letter saying "Shut up and do it- your big sister" to get Lina to agree to help Filia save the world from the prophecy of destruction - although this was after Lina had a panic attack upon receiving the letter, prompting her to quickly build and seal herself inside a coffin, in a large pyramid.
Dilgear: One day, Luna met and befriended the half-troll, half-beastman Dilgear (a former servant of her sister's traveling companion; Zelgadiss and his great-grandfather; Rezo the Red Priest) when he was wandering around looking for food. She took him in and kept him as a pet, renaming him "Spot". This is shown in an eyecatch from Slayers NEXT, shown on the right.
This eyecatch gave rise to the rumor that Luna is best friends with Greater Beast Zelas Metallium, presumably because many people mistook Dilgear for Zelas' beast form. In actuality, Luna and Zelas would probably be enemies, because the former serves the shinzoku while the latter is a mazoku.
Luna never really shows up in any of the Slayers media, and is mostly just talked about (especially in TRY). She does however, make brief cameos in the Slayers Special manga (Episode 19: To Catch a Thief), the Slayers Super-Explosive Demon Story manga (Chapter 27: Commandment Investigation Part 2), and in the opening theme songs of NEXT and TRY, as well as in a group shot in one of the eyecatches in episode 13 of Evolution-R (unlike her other depictions, her hair is not violet but a deeper shade of crimson). According to Hajime Kanzaka, Luna's involvement in a story could greatly upset the balance of the cast, which may be part of why she did not make an appearance to date.