Solitär

Solitär (ソリテール) is an eccentric demon who conducts research on many living creatures, including humankind. She seemed to have a personal connection with the Demon King. Macht of El Dorado once encountered her while searching for answers to his questions about humans. Although she appears unassuming, Solitär is hinted to be an extremely powerful demon, comparable to the likes of the Seven Sages of Destruction.

Personality
Solitär is stated to be an eccentric demon who engages in research on living beings, unlike the majority of demons who devote their lives to battle and improving their magic. She seems to have intimate knowledge of biological life forms, even being aware of complex scientific theories, such as the theory of evolution, and understands the differences between different living species, such as the shark and the orca. Unlike most demons, she owned a living quarters, which she repurposed from that of humans, where she stored her research materials and animal specimens.

Solitär appears to be amiable and friendly towards others, even when her hospitality is not returned. She was willing to receive Macht and answered his questions genuinely, even though she believed them to be pointless and trivial. She is knowledgeable about people and their behaviors, and even replicates them in her daily life even when she is not in the presence of humans. Even though it was not necessary and not reciprocated by the other, she still invited Macht to her house and served him tea and sweets which he did not consume. Solitär also seems to understand, on some conceptual level, emotions exclusive to mankind, as evidenced when she used the phrase "to hurt one's feelings" on her own without any external prompt. Even though she went on to say those were emotions demons would never be able to understand, it is reasonable to think that Solitär must have some understanding of these concepts to be able to use them herself. It is possibly why she appears to take great interest in Macht, who wished to attain coexistence with mankind through understanding their emotions, calling him fascinating.

She seems to hold great respect and even fear towards the abilities of humankind, claiming she was too cowardly, scared and not wise enough to ever disrespect them. This means she holds the potential of people extremely highly. She extends the same respect towards the magical achievements of mankind, as she described the numerous magic theories embedded within the Great Barrier of El Dorado and expressed her regret having to destroy it.

Appearance
Solitär looks like a young girl. She has long and unevenly cut hair which reached past her torso, a round face with large eyes. Her horns are small and located slightly above her forehead, separating her front bangs. She wears a necklace with a tube-shaped pendant in front of her chest.

When she met Macht, Solitär was wearing a sleeveless light-colored dress consisting of two lapels. She had bracelets on both of her hands and wore some kind of sandals with ribbons. In the present day, she wears an additional darker colored cardigan on top of the outfit above.

History
Solitär is an eccentric demon who is interested in researching natural life. She was directly acquainted to the Demon King, who had taught her the concept of convergent evolution. Although unclear, her words in Chapter 94 implied she had had close encounters with humankind, prompting her respect and fear towards them.

Around a century ago, Macht of El Dorado came to find her with questions about emotions exclusive to mankind. She told him that demons would never be able to feel those emotions, but Macht was not deterred. He even expressed the wish to coexist with people once he became able to feel those emotions. Solitär was fascinated by the demon's preoccupation with coexistence, calling him interesting. She later introduced Macht to humankind's magic.

She is implied to have been the demon to singlehandedly destroy a Fortified City in the northmost area of the country, the event which resulted in Macht being equipped with the Stone Bracelet of Sovereignty.

She reappears again at the Great Barrier of El Dorado a century after her first meeting with Macht with the intent to assist his escape and witness the ending to the latter's pursuit.

Abilities
Solitär is implied to be an extremely powerful demon; a great demon comparable to the likes of the Seven Sages of Destruction, who was capable of felling a Fortified City by herself. Fern also noted for a split second that she possesses an incredible amount of mana.

Human magic: as part of her research, Solitär is proficient in human magic. She appears to have a large collection of grimoires. Macht credited her as the person whom he learned human magic from. She is capable of deciphering magic barriers created by humans.

Trivia

 * Solitär means solitude. As per her namesake, she prefers to live on her own and spend time on her research.