Myurran, also known as Mjur Farmenas, is a major supporting character who originally lived as a witch in the Jura Forest. For three hundred years, she resided there in isolation, devoting herself to magical research and keeping her distance from both humans and other beings due to the persecution she faced. Her deep fear of death and desperate wish for more time led her to accept an offer from the demon lord Clayman. This decision, however, trapped her under a cursed spell called the Marionette Heart, which turned her into an unwilling puppet forced to follow Clayman's commands. She became known as the Ring Finger among his Five Fingers, a title referring to her role as one of his direct agents.

Myurran possesses a highly responsible and careful nature. She is meticulous in her planning and approaches every task with strategic forethought. Despite her initial alignment with Clayman, she is not inherently malicious. Her actions are driven by her circumstances and the curse that robs her of free will. Internally, she harbors a strong desire to be free from her servitude and deeply regrets the harm she is forced to cause.

Her role in the story begins when Clayman sends her to infiltrate Rimuru Tempest's nation of Tempest. She disguises herself and approaches Youm Farmenas, a human mercenary leader allied with Rimuru, by asking to join his security corps. During her time with Youm, she develops a genuine romantic bond with him. This relationship becomes a turning point, as it causes her to question her loyalty to Clayman and the orders she has been given. When Clayman's attack on Tempest is launched, she is compelled to activate a magical barrier that suppresses all magic use within the city. This action leads to devastating losses, including the deaths of several of Rimuru's citizens, notably Shion. Witnessing the suffering she has caused pushes her to rebel against Clayman, even knowing it could cost her life.

After the attack, Myurran is confronted by Rimuru and his allies. Rather than executing her, Rimuru recognizes her genuine remorse and chooses to spare her, offering her a second chance. This moment marks the beginning of her redemption. She takes up residence in Tempest alongside Youm, contributing her magical knowledge to the reconstruction and strengthening of the federation. Over time, she becomes a trusted member of the community. She later marries Youm and becomes the first queen of the newly renamed Farmenas Kingdom, with the couple eventually having a daughter named Mieme.

Her key relationships are central to her development. Youm is her anchor, and their bond is built on trust, sacrifice, and mutual growth. Through him, she finds a reason to fight for something beyond mere survival. Rimuru is the one who grants her forgiveness and freedom, reinforcing the theme of second chances. Clayman is the source of her initial suffering; she resents him for the curse and the control he exercised over her, though alternative timelines explored in spin-off material show that under different circumstances, she could have developed genuine loyalty toward a better version of him.

In terms of notable abilities, Myurran is a powerful and knowledgeable mage with centuries of magical research behind her. She is skilled in barrier magic, having the capacity to conjure a field that nullifies other magic users' abilities across an entire city. She also possesses the ability to disguise her appearance to blend in among humans. After evolving into a demon and later ascending to a position of royalty, her magical prowess continues to grow, though her strength lies more in strategic and utility magic than in direct combat.