Blei is a male human mage who participates in the First-Class Mage Examination, a significant test for magic users in the world of Frieren: Beyond Journey's End. He is a member of the Seventeenth Party during the first stage of the exam, alongside his companions Edel and Dünste.

Physically, Blei is a tall man with a shaved head and a goatee. His attire consists of long, light-colored robes secured at the waist with a rope, worn beneath a long black overcoat, and he also wears a light-colored cowl around his neck. This outfit, combined with his bald head, gives him an appearance reminiscent of a monk.

In terms of personality, Blei demonstrates a composed and level-headed demeanor, even when faced with stressful situations. He is depicted as cooperative and disciplined, generally following the orders of his party member Edel without complaint. Blei is not afraid to question authority, as seen when he directly asks the proctor, Sense, if she intends for all examinees to fail the second stage of the exam. His rational nature is evident when his party is cornered by a magical clone; he calmly assesses their situation, noting that they cannot hide indefinitely and must eventually fight. While Edel claims he cannot imagine defeating their powerful opponent, Blei remains optimistic, searching for a strategic solution. Perhaps his most defining trait is his self-sacrificial nature, as he chooses to stay behind and hold off an enemy clone to give his companion Dünste a chance to escape.

Blei's motivations and role in the story are centered on his participation in the First-Class Mage Exam. During the first stage, his party's strategy involves waiting by a lake to capture a rare bird called a Stille. When another examinee freezes the lake, Blei follows Edel's instruction to melt it by shooting a continuous stream of fire at the ice. Although their initial plan is disrupted, the Seventeenth Party successfully captures a Stille, allowing them to pass the first stage. In the second stage of the exam, held within a dangerous, unmapped dungeon, Blei questions the proctor about the lethal nature of the ruins. Inside, his party is hunted by a magical Spiegel clone of the proctor, Sense. When their attempts to fight or evade the clone fail, Blei makes the decision to sacrifice his own chance to pass the exam. He tells Dünste to escape while he holds the clone back, after which he breaks his escape golem, signaling his own failure and removal from the dungeon.

Blei's key relationships are primarily with his exam party members, Edel and Dünste. He respects Edel's leadership and strategic mind, often deferring to her judgment. His bond with Dünste is particularly strong, as he ultimately sacrifices his own success to ensure Dünste's survival. Regarding character development, Blei's journey is brief but showcases a shift from a pragmatic exam participant to a selfless individual who prioritizes a comrade's safety over his own goal of becoming a first-class mage.

As for notable abilities, Blei is a practitioner of modern magic, which typically involves manipulating or changing pre-existing elements. He demonstrates this by casting a powerful fire spell in an attempt to melt a frozen lake. While not much else is known about his specific skills, he is able to hold off the Spiegel clone of Sense for a crucial period, allowing Dünste to flee. However, Edel notes that he cannot even fight properly within the dungeon, suggesting that his abilities are limited in environments where the elements he manipulates are not present. The name Blei is the German word for the metal lead.