Echidna is a Wild Elf, hailing from a rare tribe distinct from the forest elves typically seen, with her home in the southern jungles of the continent. She has lived for well over five centuries, giving her an immense wealth of battle experience. Standing approximately 162 centimeters tall, she has dull green hair with whitish bangs and sharp red eyes. Her distinctive outfit consists of a white, open breastplate with a snake-themed collar, and she is well known for using her pet snake, a magical creature named Keltan, as a living belt or thong, effectively wearing no other underwear. A curved snake-themed sword and a small buckler shield are her primary weapons, though she also wields a dagger.

In terms of personality, Echidna presents a complex and often contradictory nature. She is commonly perceived as cruel, perverted, and sadistic, frequently invading the privacy of attractive women and subjecting them to unwanted groping and humiliation, with a particular interest in Leina Vance. She expresses disdain for the long-winded sermons of more conventional forest elves like Alleyne. However, beneath this harsh exterior, she hides a secret bright side and a heart of gold. She can be surprisingly pure, gentle, and vulnerable, even to the point of crying when emotionally overwhelmed. This duality is a core part of her character; her actions, while seemingly erratic, often have a deeper, hidden meaning.

Echidna works as a freelance mercenary, a lone wolf who was once the leader of the infamous Fang Assassination Unit. Her primary role in the story is as a supporting character who becomes a mentor to the protagonist, Leina Vance. She is hired to keep an eye on Leina, but her methods are unconventional, including forcing Leina into an underground fighting arena to test and train her. Despite being considered a favorite to win the Queen’s Blade tournament due to her incredible skill, she has no personal interest in the throne or the title of Queen. Her motivations for participating in the tournament remain largely unclear, though they are suspected to be tied to her past as a hired soldier or a personal contract.

Key relationships define much of her development. She was the former master of Irma, another deadly fighter whom she rescued as a child and trained in the ways of an assassin. Their relationship is fraught with tension, as Echidna abandoned Irma during a mission to save herself, leading to deep feelings of resentment and a desire for revenge from her former pupil. Despite this, Echidna still harbors genuine care for Irma, ultimately choosing to save her life over completing a mission and showing visible emotion when Irma is hurt. Her primary interest in Leina is a mix of predatory flirtation and genuine investment; she finds Leina refreshing and is amused by her strength, offering training and aid while also secretly acting as a protector. A crucial piece of information she holds is the knowledge that Queen Aldra was responsible for killing Maria Vance, the mother of Leina, a secret she keeps hidden from the Vance family throughout the main series.

Echidna is an exceptionally agile and skilled warrior, considered practically invincible in individual combat. Her fighting style is coldly efficient, focusing on precision strikes and psychological manipulation. Her signature technique is called the Black Rose, where she parries an enemy's attack with her sword and immediately counterattacks with a dagger in her other hand. She also utilizes her pet snake, Keltan, as a weapon; the snake is venomous and can be used to deliver debilitating bites to her opponents. Her combat parameters are exceptionally high, with maximum ratings in defense, technique, and agility.