Heiter is a human priest who served as a key member of the Hero Party that defeated the Demon King. He was a childhood friend of the hero Himmel, and the two left their home village together to embark on their decade-long quest. As a veteran of that legendary journey, Heiter played a crucial supportive role, using his holy magic to protect and sustain his companions.

Heiter presents an intriguing contrast between his sacred vocation and his personal vices. He is known for a cheerful and outwardly laid-back disposition, often using humor and laughter to diffuse tense situations. His most defining flaw is an exceptional love of alcohol; during his adventuring days, his drinking would frequently lead to severe hangovers, rendering him useless for about a day each week. This unpriestly behavior earned him the teasing nickname of "corrupt priest" from the elf mage Frieren. Despite this sloppiness in his private life, those who know him well recognize a sharp, shrewd, and deeply responsible individual. He often played a guardian-like role within the Hero Party, scolding Frieren for her laziness with parental firmness. Inwardly, he could be cynical about their chances of success, doubting his own abilities, but he resolved to place his absolute faith in Himmel's leadership. His faith is genuine and provides him with a comforting perspective; he believed that the end of a life lived earnestly cannot be nothingness, and he offered this gentle view of death to ease the hearts of his companions like the warrior Eisen.

In his later years, long after the Demon King's defeat, Heiter traveled to the Holy City and rose through the clerical ranks to become a bishop, earning widespread respect as a great priest. Even in this position, he maintained strong bonds with his former comrades, continuing to exchange letters with the dwarf Eisen until the end of his own life. Heiter eventually retired from his official duties and lived in a remote region, where he encountered a young war orphan named Fern in the Southern Lands. Taking her in, he became her guardian and foster parent, demonstrating his most profound transformation: he gave up alcohol entirely to raise her properly, sacrificing his health for her future. Aware that his own death was approaching, Heiter devised a plan to secure Fern's future. When Frieren came to visit, he asked her to decipher an old grimoire, a task he knew would take time. Under this pretense, he persuaded Frieren to take Fern on as her apprentice, ensuring the girl would be trained as a mage and have a companion for her journey. After confirming that Fern had grown capable, Heiter passed away peacefully from old age around the age of one hundred.

In terms of abilities, Heiter was extraordinarily powerful, wielding the Goddess's magic with a level of skill and mana reserve that even the millennia-old Frieren found astonishing. His mana pool was immense; in his youth, he estimated that Frieren, who was deliberately suppressing her power, had only a fifth of his own mana. This would place his power as a teenager on a level comparable to a mage with five hundred years of training, rivaling that of great demons like Aura of the Seven Sages of Destruction. He was also notable for being one of the few individuals capable of detecting that Frieren was restraining her mana at all. His practical feats of magic included maintaining a long-lasting blessing on the entire party that allowed them to survive for two months without food, water, or oxygen, a spell Frieren herself described as monstrous. He could perform healing magic, use offensive spells like the Three Spears of the Goddess, and cast stealth magic to prevent mana detection. His natural vitality was also remarkable, as he lived to an advanced age for a human despite his long history of heavy drinking.