Carmilla

Carmilla (カーミラ) was the Witch of Lust. She formally debuted in Arc 4 as a supporting character.

Following her death 400 years ago, Echidna collected her soul and brought it to the Sanctuary along with the other witches. Throughout Arc 4, she and the other witches helped Subaru accept himself and change his views on Return by Death. After the arc, her soul was transferred into a crystal and she is currently travelling with Omega.

Appearance
Carmilla is described as giving off a fragile impression. She has long, light pink hair that goes down to her hips. She has a very refined face with round, red eyes. Her appearance is described as uncommonly adorable rather than being standout beautiful, considering she's the Witch of Lust. She wears a muffler wrapped around her neck which is long enough to touch the ground. She is very averse to exposing her skin, hence she likes to wear long sleeved clothing. She is usually seen in a snow-white dress that completely covers her body, leaving only her face exposed. Carmilla often acts very timidly, having an extremely frail look in her eyes, which ticked Subaru off.

Personality
Carmilla has extremely low self-confidence, often having downcast eyes and overall acts very timid. She tends to stutter and question her own words, more often than not ticking other people off by doing so. She speaks in a very polite manner, trying not to cause any disagreements or disapproval. At times, she shows a rather submissive side of her, when dealing with her fellow Witches of Sin, as seen when she had no problem it taking part of Echidna's scheme to lure Subaru into her castle of dreams, despite knowing it will end badly for her. Due to her timid personality and low self-confidence, she is frequently seen shying away from stern gazes, often pleading people not to hit her or exercise any form of violence towards her which likely stems from her past bad experiences with other people.

According to Echidna, Carmilla only cares for herself and holds deep grudges if you were to harm or trick her in any way regardless if she's in the wrong.

In the past, Carmilla was the reason why her village, the neighboring villages and cities and even the great country she lived in, were engulfed in the flames of war. Everyone desired and loved her but she desired none of it, hence she left everything and everyone behind in search of the love she lost.

History
A long time ago, Carmilla was a normal girl who was loved by the people in her village and even had a fiancé. However, one day a man of power came to the village and desired her. Angered by the man's actions, the villagers rose up in defiance and fought against him, eventually burning him with his mansion. The cities and villages around theirs began to regard them as dangerous, causing the fighting to spread, and soon their force was toppling countries, all the while claiming that it was for her sake. Carmilla began to be regarded as a heavenly maiden, nevertheless, she didn't desire such a thing, and saw that they were being misled by their own fantasies and manipulated by their ideals. After they had toppled a large country, her fiancé proposed to her at the top of the castle, though she ignored him and left everything behind, despairing that what she had originally wanted no longer existed.

It is said that over 400 years ago, Carmilla burned to death. Like with the other Witches of Sin, Echidna located her soul and collected it, allowing Carmilla to manifest in the castle of dreams, alongside her deceased friends.

Abilities
Authority of Lust (色欲の権能 Shikiyoku no Ken'nō): Carmilla is able to use the Authority of Lust.
 * Faceless Bride (顔のない花嫁 Kao no nai hanayome) Carmilla can captivate people, making them so absorbed in watching her that they forget how to breathe, lose all sense of awareness to the point they wouldn't notice if someone stabbed them or if they were burning and in the vast majority of cases, their heart stops beating which results in their death without them even being aware of it. She can also cause people to see and hear her as what they want to see and hear, such as when Subaru saw and heard her as Rem.
 * She also seems to be capable of making people "understand feelings" like love, as seen in the Witch's Tea Party when she used her Authority of Lust to help Subaru understand Satella's love for him.

Trivia

 * According to the author, Carmilla's birthday is June 19.
 * Carmilla's name refers to the 107 Camilla asteroid, one of the largest of the main belt asteroids. In Roman mythology, she was the daughter of King Metabus and Casmilla.
 * Her name may also be a reference to Carmilla, a lesbian vampire from the story of the same name who seduced and obsessed over her victims.
 * Due to Carmilla's lack of fighting abilities, she had personal guards who protected her. The author also noted these guards were able to resist her Authority to some extent because they had "tough hearts".
 * Very few people actually met Carmilla and got to walk away with their lives, due to her Authority of Lust.
 * Carmilla does not have any interest in love, nor does she wish to love or be loved by others (likely due to the events from her past).
 * If Carmilla and Capella were to fight to the death, it would conclude with Carmilla's victory (barely but surely).