In the anime I'm a Noble on the Brink of Ruin, So I Might as Well Try Mastering Magic, Radon is a magic dragon of immense power who becomes central to the protagonist's life. Long ago, Radon was sealed away by the ancestors of the Hamilton noble family, and for years she existed mainly as a legend connected to the family's history. When the seal was broken during an attempt by Liam's eldest brother to claim glory by defeating the dragon, Liam rushed to the forest where the encounter took place and faced Radon directly. Instead of resealing her, Liam reached an arrangement with the dragon: Radon would lend him her formidable strength and, in exchange, take up residence within his body. Impressed by Liam's overwhelming magical capacity, Radon becomes his familiar and one of his most important allies.

Radon is female, and because she is extremely long-lived she carries an old-fashioned, formal manner about her that sets her apart from younger characters. In her natural form she is a huge and imposing dragon, but she also possesses the remarkable ability to manifest an avatar in the shape of a young girl. This human form reflects her true gender and looks nothing like what one would expect from a magic dragon. She uses it to accompany Liam in everyday situations and to interact with other people, often surprising those who know only her fearsome reputation.

In terms of personality, Radon is haughty and mischievous toward most people, but she is fiercely loyal to Liam. She serves as his mentor in ancient magic and shares knowledge about magical theory and the history of the world that has been lost to time. She frequently nudges Liam to think of new spells in order to solve whatever problem is at hand, and Liam regularly consults her about various troubles. Radon also gives him tasks, such as taking over the protection of a group of pixies that she had been guarding in the forest where she was sealed. Her combination of deep knowledge and playful pride makes her both a reliable guide and a source of friction with others.

Radon's role in the story is closely tied to Liam's rise as a mage. The power she lends him and the ancient wisdom she provides are major reasons Liam is able to grow beyond ordinary human limits. She acts as his companion and protector, and her presence becomes a defining part of his identity. When Liam establishes his own country, Radon is the one who gives it its name, and the nation becomes known as the Kingdom of Liam Radon. Because the two are so strongly linked, other kingdoms come to see them as a single unit, and proposals such as a strategic alliance between Liam and Radon are brought directly to them by foreign powers.

Over the course of the story, Radon develops from a solitary, sealed-away entity into a dedicated partner who takes genuine interest in Liam's unconventional approach to magic and in the community that grows around him. Her nature also carries a distinctive trait: all dragons of her kind are female, and they reproduce asexually through magic. The offspring produced in this way are known as the Radon Jrs, and they are truly her own children, which expands her role as a figure of great lineage and power.

Among her notable abilities are her vast magical strength, which she lends to Liam from within his body; her capacity to take on a human girl's form as an avatar; her expertise in ancient magical arts; and her knowledge of the world's forgotten history. In her true dragon form she can show Liam displays of her full power, underscoring the scale of what she commands and the value of having her on Liam's side.