Flandre Scarlet

Flandre Scarlet is the younger sister of Remilia and the "dirty little secret" of Scarlet Devil Mansion. Because of her unstable personality and incredible destructive power she lives in the basement of the mansion. She's immune to Holy things and has incredible physical strength; her sister has ordered her not to leave the mansion for nearly 500 years. She knows little about the world outside and, until the heroines arrived during the Extra Stage of Embodiment of Scarlet Devil, she has had no substantive contact with any humans other than Sakuya.

Appearance
She has red eyes and short blonde hair, which is tied into a single ponytail on her left side. Wears a red skirt and vest, with a pink shirt underneath. Also wears a pink mob cap with a red ribbon attached. Her wings appear to be made of iron and prism shards. She carries a matching metal wand with her, which is apparently the mythical Lævateinn. Arranged from her back to the tip of her wings her 8 crystals are presented as follows: Light Blue, Blue, Purple, Pink, Orange, Yellow, Light Green and Light Blue again. Has longer hair than Remilia.

Power
Flandre Scarlet is possibly one of the most powerful beings in Gensokyo. In addition to the massive physical and magical strength of a vampire, she possesses the ability to destroy anything by finding and crushing its "eye" in the palm of her hand. The "eye" is a sort of center of tension present in anything. The limits of this ability are unknown. It is known that once she destroyed a meteor that would have crashed into the Scarlet Devil Mansion.

Flandre has other miscellaneous powers she uses in spellcard combat, such as the ability to create three duplicates of herself and to turn invisible. She wields Laevateinn, a metal staff which can turn into a massive flaming sword that leaves trails of small fireballs behind it when swung.

Flandre can turn into a bat to avoid dangerous attacks. Interestingly, her bat form's wings are normal, rather than the crystal wings she normally has.

While it is a matter of course, she has the destructive power of oni and the nimbleness of tengu, as well as a vampires bodily and regenerative ability. She somehow exceeds even her older sister Remilia Scarlet.

Personality
Flandre is somewhat insane (her official profile describes her as "kind of nuts". This in combination with her immense power leads the residents of the mansion to typically keep her inside. Despite this, she is usually docile and doesn't try to get out by force, even though with her power she probably could. Therefore it's probable that she is a shut-in of her own will. She is said to respect her older sister a lot.

Flandre is incapable of feeding herself like most vampires, because due to being locked in the mansion she doesn't know how to properly subdue a human to drink their blood. When she tries to attack a human, she vaporizes them completely, leaving no blood left to drink. She depends on Sakuya to feed her.

Relationships

 * Remilia Scarlet (Older sister)
 * Patchouli Knowledge (Sister's friend)
 * Sakuya Izayoi (Chief maid)
 * Hong Meiling (Gatekeeper)
 * Koakuma (Unknown)
 * Marisa Kirisame (Known)
 * Reimu Hakurei (Known)

Fan culture

 * Flandre's personality is the subject of a lot of controversy among fans. Depictions of her vary from a tragic figure unjustly imprisoned by a jealous and insensitive sister, to an unstoppable juggernaut of death and carnage that obliterates everything in her way. Usually she is portrayed as a playful little girl with a sinister side, as her playmates always risk of getting broken.
 * There is some speculation regarding why her wings are the way they are.
 * Some consider the crystals on her wings to be the source or the seals of her power.
 * Flandre is often depicted as bipolar, one personality being childish and playful, the other brutal and sadistic.

Trivia

 * A silhouette of Flandre occupies the front of Embodiment of Scarlet Devil's jewel case.
 * Assuming her birth year by calculating backwards in the Gensokyo Timeline, she's supposed to be born around 1508 A.D. But the "canon-ness" of this assumption is unknown.
 * Her boss theme ("U.N. Owen was her?") and her second-to-last spell card ("Secret Barrage - And Then There Will Be None?") are references to Agatha Christie's novel And Then There Were None.It's more speculative but still worth noting that the science-fiction genre saw Philip K. Dick write a novel called "Counter-Clock World" in 1967 and Frederik Pohl write "The Gold at the Starbow's End" in 1972.
 * Her sword/wand Laevateinn is, or shares its name with, the sword/wand of Loki, Norse god of Mischief and Chaos. (Her sister Remilia, in turn, uses Gugnir, the mythical spear of the Norse god Odin).
 * On one end of the Lævateinn that Flandre is seen holding in Shoot the Bullet is very different compared to the Lævateinn that Flandre is seen holding in Embodiment of Scarlet Devil.
 * Flandre's wings have an unusual appearance which bears almost no resemblance to a vampire's typical bat-like wings (or even organic matter).
 * The "crystals" on her wings look somewhat similar to the crystals shown on Patchouli Knowledge's spell card, Fire Water Wood Metal Earth Sign "Philosopher's Stone".
 * Strangely, if one uses a bomb against her in Embodiment of Scarlet Devil's Extra, she's shown to have normal wings in bat form.
 * In Chapter 9 of Inaba of the Moon and Inaba of the Earth, Reisen Udongein Inaba and Tewi Inaba get lost in the Scarlet Devil Mansion and end up being chased by what looks to be the silhouette of Flandre.
 * Her theme song, U.N. Owen Was Her? has gained tremendous popularity through a remix of it using sounds from Japanese McDonalds commercials called McRolled. Most Western fans of Touhou Project first learn about the games through the McRolled videos. Since McRoll is more popular than the original tune, many trolls will try to enrage Touhou fans with the saying "ZUN stole from McRoll".
 * A remix of her theme uploaded on Youtube under the incorrect name of "John Stump - Death Waltz" gave the theme even more popularity and led to even more confusion, many people now believing "Death Waltz" is the correct name of the theme (or that "U.N. Owen Was Her?" was based on "Death Waltz"). In addition, the remix has become infamous for the utter impossibility for anything other than a computer to play it, so another popular upload of the same remix simply labels it as "the hardest song of all time".