Leif Ericson is a retired explorer and adventurer who lives on Greenland and is one of the few people to have reached the distant land of Vinland. He was a close friend of Thors Snorresson and becomes a key figure in the life of Thors' son, Thorfinn. Leif is based on the historical Norse explorer of the same name, and the series presents him as a figure who embodies exploration, peace, and loyalty rather than combat.

Leif's background is that of a seasoned traveler who endured great hardship. During his early voyages, his ship crashed into an iceberg, and he lost all six of his crew members to the harsh cold before he eventually discovered Vinland. He successfully made peace and traded with the native people there, and he received gifts such as a smoking pipe and a headdress from them. He is a Christian who traveled across the Atlantic, and he often told stories of his adventures to the children of his town.

Leif's personality is characterized by a cheerful, kind-hearted, and wise nature. He is known for his adventurous spirit and his willingness to help others, which earned him the nickname Leif the Lucky. He can sometimes come across as brash, but he always has the best interests of those around him in mind. He is loyal by nature and places great value on trade and reconciliation rather than violence, a trait that sets him apart from many other Norse characters in the story. He is also known to slightly exaggerate his stories to captivate his audience.

Leif's primary motivation is his deep sense of responsibility and loyalty. After Thors was killed and Thorfinn went missing, Leif blamed himself and made it his mission to find Thorfinn and bring him home. He spent over a decade searching for him, driven by a desire to repay a debt to Thors and to protect the boy he felt he had failed to watch over. He never gave up hope of finding Thorfinn, even after many years.

In the story, Leif serves as a mentor and a guiding figure for Thorfinn. He first appears telling stories of Vinland to the children, which sparks Thorfinn's dreams of a peaceful paradise. After Thors' death, Leif becomes the one who tirelessly searches for Thorfinn. He encounters Thorfinn years later and tries to bring him back home, but Thorfinn refuses, still consumed by vengeance. Leif promises to wait for him. He later tracks Thorfinn down again after he is sold into slavery and works to free him, finally fulfilling his quest to bring him home after sixteen years. He acts as a bridge between Thorfinn's past and the promise of a better future.

Leif's key relationships are with Thors, whose friendship he cherished, and with Thorfinn, whom he treats with great care. He also has a bond with the people of his community, who love him for his wisdom and passion. He forms a comedic bond with a young man he adopts and gives the name Thorfinn during his search. Leif's relationship with the protagonist is central to the story's themes of redemption and hope.

Leif's character development is subtle but significant. He begins as a storyteller who warns Thorfinn of the dangers of the sea, acknowledging his own past traumas. After Thors' death, he transforms into a determined seeker, driven by guilt and love. His long search for Thorfinn shows his growth from a passive storyteller into an active protector. He ultimately finds peace when he succeeds in bringing Thorfinn back to his family, allowing the younger man to take the spotlight.

Leif's notable abilities are not in combat but in navigation, exploration, and diplomacy. He is a skilled sailor who successfully made the difficult journey to Vinland and back. He is capable of making peace with foreign peoples, as shown by his friendly trade with the native inhabitants of Vinland. His greatest ability is his unwavering perseverance, demonstrated by his sixteen-year search for Thorfinn.