Echidna is a wild elf from the southern tropical forests, belonging to the distinct tribe known as the Wild Elves. A veteran mercenary with over five centuries of battle experience, she once led the infamous Fang Assassination Unit. Though her strength and reputation make her a formidable contender, she has no desire to win the Queen’s Blade tournament or claim the throne, participating only for unknown employers or personal motives. She has dull green hair with whitish bangs, red eyes, and stands 162 cm tall. Her attire includes a white vest-like top with a snake-themed collar, turtle shell shoulder plates, and a red gem on each breast. Rather than conventional underwear, she wears her pet snake, Keltan, coiled around her waist, along with white shin-guards and dull green thigh-highs. In her Unlimited form, her skin darkens, her hair turns white, she grows to 168 cm, and her outfit and sword undergo subtle changes. Echidna displays a cold, cruel, and sadistic exterior, often paired with highly perverted behavior such as flirting with and groping women she favors, especially Leina. This two-faced nature conceals a compassionate and kind-hearted core; she secretly helps those in need and holds deep loyalty toward former students. She prefers traveling alone and enjoys sleeping nude. In combat, she is regarded as nearly invincible, combining superhuman agility, rare skill, and unshakable confidence. She wields a curved snake-themed sword and shield, fighting alongside Keltan. Her signature technique, the Black Rose, involves parrying with her sword and countering with a dagger. She excels at psychological warfare, using mind games to unnerve opponents. Echidna trained Irma, leader of the Assassins of the Fang, raising her after the death of Irma’s brother. They shared a close bond, including sleeping together during training, until a broken promise created a rift. Despite Irma’s grudge, Echidna still cared for her, and they eventually reconciled. Later, they settle down together, caring for cats. She maintains a rivalry and occasional partnership with Risty, rooted in mutual respect and profit. With Alleyne, a forest elf, interactions are marked by teasing and cultural tension. Echidna also trains Leina, pushing her to grow stronger through methods involving teasing and inappropriate contact. In other media, such as the Vanquished Queens OVA, Echidna acts ruthlessly, threatening to rape the amnesiac Aldra to trigger her latent powers—a deed she follows through in an alternate ending. In Queen’s Blade: Limit Break, she appears as a playable character with variants like "Serpent Elite" and "Battle-Hardened Mercenary." Throughout her appearances, Echidna remains a lone wolf mercenary, accepting missions that align with her interests or hidden morals. Her journey reflects a balance between her harsh profession and inner kindness, influencing others through mentorship and action. She ultimately finds peace and companionship, leaving solitude behind.