Sylvia Lyyneheym (シルヴィア・リューネハイム) is the student council president of Queenvail Girls' Academy and the world's most famous idol.
Sylvia has long purple hair and purple eyes. She is breathtakingly beautiful. Despite her appearance, she is very strong, having won second place in the previous Lindwurm losing only to Orphelia.
Sylvia can use the headphone shaped hair accessory she wears to change her hair color. While in disguise, Sylvia has brown hair which she ties together. She hides her headphone shaped hair accessory under a hat.
Sylvia is bright and popular as she is the most famous idol in the world. She is playful around Ayato but understands how important her public appearance is.
Strega (魔女): Sylvia can use her singing to manipulate mana and control her surroundings, which makes her abilities as a Strega versatile as she isn't bound to a particular image. However, she has to write the song herself, she can't use any healing abilities, is limited to one ability per song, and her prana usage varies depending on what ability she is using, with her mentioning that using a time control ability similar to Helga's would instantly drain all of her prana.
- Search: After obtaining information about the target, Sylvia sings to locate it. Once she finishes singing, two black feathers spin around before narrowing down to a particular location. This song is titled Lonely Feather in the OST release.
- She sings, "The two pairs of wings known as thought and memory, move around move around speedily run around, hold the voice of the captive beloved child, pass the sea of clouds of the dawn, ride on the wind of twilight, open guidance from the edge of dusk, the black servant of thought and memory, come down before me and speedily show me" (思考と記憶の二対の羽よ 巡れ巡れ疾く駆け巡れ 囚われの愛し子の声を持て 暁の雲海を超え 黄昏の風に乗り 宵闇の果てより導きを開け 思考と記憶の黒き御使いよ 我が前に舞い降りて疾く示せ).
- Wind Barrier: Sylvia creates strong currents of wind around her. She used this during her battle with Orphelia to block her miasma, though it was blown away when Orphelia caused her own miasma to explode with sparks.
- She sings, (耳を澄ませ 故郷は遠く 楽園は砂塵の果て 紡ぐは風 吹き渡る風)
- Self Strengthening: Sylvia strengthens her physical capabilities. According to her, she could potentially fight and win against Ernest, who is considered to be one of the best swordsmen, while strengthened as long as he didn't use Lei-Glems. During the Lindwurm, she uses an improved version of the song that would allow her to fight on par with the current Ayato.
- She sings, (ぼくらは壁を打ち崩す 限界の先に境界を越え 傷を厭わずに 走れ 走れ). Later on, (想いだけでは追いつけないから 願うだけでは超えられないから 力の限り その先へ) is added.
- Valkyries: Sylvia creates shining Valkyrie shadows with wings and a sword. She created 100 of them during her battle against Orphelia, however none of them were able to deal any damage to Orphelia due to her high prana levels.
- She sings, (讃えよ 讃えよ 英霊の凱旋を 銀の煌きを 軍門は今 我らが前に 天は道を示し 祈りは剣に 願いは刃に 雄渾の歌よ高らかに！)
- Wings of Light: Sylvia creates wings of light that allow her to fly.
- She sings, (蒼穹を駆け 渾天を巡る意志の翼は いつの日かキミを 明日の向こうへ導くだろう)
Genestellar (星脈世代): As a Genestellar, Sylvia has enhanced physical ability and an aura known as prana.
Lux: Sylvia uses a custom made Lux known as Folkvangr (フォールクヴァング).
Sylvia enjoys teasing him. After being rescued by Ayato, she develops a crush on him. Her feelings become serious after Ayato pledges to help her solve her problem with Ursula Svento.
- According to the author, Sylvia's birthday is October 1st, her horoscope is Libra, and her blood type is O.
- Sylvia is famous enough that people who don't care about trends such as Ayato know who she is.