Echidna

Echidna is the demon queen leading the latest invasion on mankind in search of the Philosopher's Stone. After being defeated by Leo Demonheart, she was driven into retreat, but seeks to rebuild her army.

She is the titular female protagonist of the Yuusha, Yamemasu series.

Appearance
Echidna is a woman of average height. She has horns, knee-length pink hair, and deep, golden-colored eyes. She wears one pair of red earrings, thigh-high boots, a red dress, and a black belt adorned with a golden suspender. Even though she has a young and beautiful woman's appearance, she is over a hundred years old.

Personality
It is said that she is an unruly and cruel person. Despite these rumors, Echidna is generally easy-going, cheerful, and relaxed. As long as she isn't directly provoked, she's perfectly fine with "live and let live," although she occasionally voices the desire to burn up people en-masse when she gets impatient. At her core, Echidna is a very kind and noble woman. The reason she pursues the Philosopher Stone is because she wants to help the Demon World and give her fellow demons a peaceful place to live free of fights and bloodshed. Unlike her predecessors, she dislikes unnecessary violence. This is shown during the invasion of the human world: to keep casualties to a minimum, she gave the order to avoid killing whenever possible and rule the occupied territories peacefully.

Echidna deeply cares for her subjects and does her best to treat them with respect and kindness, taking time to thank even the lowest level subordinates for their efforts. She even organized a private dinner for Lord Onyx because wanted to personally meet and thank him for his work despite being a newbie in their army. Despite maintaining the affect of a commander in public, she has a soft spot for her generals, worrying about their problems and safety. This is especially true for her second-in-command Steina, having known her the longest.

Although she is prepared to destroy mankind in order to retrieve the Philosopher's Stone, Echidna has nothing against them. She doesn't blame them for considering her army villains. She does not discriminate among humans and treats them all with respect, and she'll welcome any who wish to join her army. The one exception to her kindness is Leo Demonheart, the lone destroyer of her army: it is for that reason she refuses to accept him when he applies to join her ranks. She gets incensed at the mention of his name, and blasts him with fire magic whenever she sees him. Despite this, she doesn't actually hate Leo, but understands that he was simply defending humanity when he fought her.

Though an imposing and intelligent woman, she has a bit of a childish and comedic side. This side shows when she's drinking alcohol, but she can quickly get serious again if the situation calls for it.

Background
As a child, Echidna grew up hearing tales of a legendary hero who single-handedly beat back every attempt by Demons to invade the Human World. In her youth, she would boast that she would become stronger than the legend, even though she was uninterested in becoming Queen. She was also fond of another story of a demon who tried to bring peace between her people and humanity, which fostered her desire for peace. After ascending the throne, she sought to use her influence to bring lasting peace to her realm. To acquire the Philosopher's Stone and use its power to fulfill her dream of a Demon World that is peaceful, she swallowed her kindness and raised an army to invade the human world. However, she could not completely discard her feelings, so she commanded her troops to avoid destruction and any unnecessary killing.

Leo Demonheart
On the outside, Echidna hates Leo, seeing him as the only obstacle between her and the Philosopher's Stone, the item that could bring peace to her world. However, she does not actually hate him for defending his world. After he sneaks into her army with help from her generals, he improves her army bit by bit while also trying to learn her motives for the stone. While she bonds with his alter-ego Black Knight Onyx, her disdain and distrust toward return and intensify. In the end, Leo deems her worthy of replacing him as the world's protector. After he reveals himself to her, he challenges her and the Four Generals to kill him and claim his heart; a Philosopher's Stone. Despite it being the best chance at fulfilling her dream, Echidna comes to understand Leo's feelings enough that she cannot bring herself to kill him.

Steina
Even though they're 300 years apart in age, Steina is the closest person to Echidna, and as such they have a strong rapport. As her second-in-command, Echidna tasks Steina with many impossible tasks, the latest being spearheading the rebuilding of their army. While she maintains the appearance of superior officer in most settings, she is acutely aware of how much pressure her friend endures to support her dream and worries for her. On the other side, Steina looks up to Echidna and believes in her dreams. This is why she accepts any task given to her without complaint and hides how exhausting her job is.

Lily
Lily looks up to Echidna, and despite her naiveté she does her best to support her as a general. Echidna recognizes Lili's youth, but still believes in her ability to be a leader.

Mernes
Echidna acknowledges and appreciates Mernes' abilities as a general, but she worries about him as she does everyone under her charge. However, Melnes first saw Echidna as the vehicle for revenge against the human race for the cruel treatment he suffered in life. When he saw how nice she was to the humans she conquered, he plotted to usurp Echidna and have lead the Demon Army to wipe humanity out. Fortunately, he was set back by the Army's defeat, and his feigned loyalty grew into the real thing.

Edvard
Though Edvard's stubborn and dense nature can create trouble for her, Echidna values him greatly and cares about his as much as the other generals.