Ketil is the owner of a large and prosperous farm in Denmark during the early 11th century. He is a man in his mid-forties with a muscular but soft build, long blonde hair, and a thick blonde beard, his face showing the early signs of age. He has inherited the vast estate from his father, Sverkel, and has since expanded it considerably, which requires him to pay large tributes to the crown for protection.

Ketil's personality is built on a series of profound contradictions. On the surface, he presents himself as a jovial, confident, and easy-going man. He is known for his seemingly kind and empathetic nature, treating his slaves and subordinates with a level of fairness unusual for the time. He works alongside his laborers in the fields and offers his slaves a genuine, if conditional, path to buy their freedom through hard work. He is moved to tears by the plight of two starving children who steal from him and shows reluctance when forced to administer punishment.

However, this gentle demeanor masks deep-seated insecurities and a capacity for explosive violence. Ketil has spent much of his adult life cultivating a false reputation, allowing others to believe he is the legendary warrior known as Iron Fist Ketil. In truth, he is a coward who has assumed another man's name and heroic feats to protect his farm and bolster his standing, a secret known only to his trusted guard Snake and the slave Arnheid. His own father views him as greedy and short-sighted for overextending the farm beyond his means.

Ketil’s primary motivation is the preservation of his wealth, land, and the peaceful, comfortable life he has built. He is driven by a need for security and respect, which his false warrior identity provides. He despises violence and conflict, yet he is trapped by the very society that values martial strength, forcing him to maintain a facade of toughness he does not possess. His apparent kindness towards his slaves is sincere up to a point, but it is ultimately conditional on his own sense of control and ownership.

In the story, Ketil acts as the master to the protagonist Thorfinn and his fellow slave Einar, providing the setting for their character development. His role is to deconstruct the idea of a "benevolent" slave owner, illustrating how even a seemingly kind master wields absolute, corrupting power over other human beings. He is also a key figure in King Canute's political machinations, as the king seeks a pretext to seize Ketil's wealth to fill the royal coffers, setting the stage for a violent confrontation.

His key relationships are fraught with complexity. With his sons, Thorgil and Olmar, he is a source of false inspiration. Thorgil, a violent and experienced warrior, idolizes the fake legend of his father, while Olmar is pushed to live up to a reputation Ketil never earned. His relationship with his slave Arnheid is the most telling; he depends on her emotionally and has been sexually exploiting her, all while refusing to allow her the freedom he offers his other slaves. When she attempts to escape with her true husband, Gardar, Ketil feels a deep personal betrayal, revealing that he views her not as a person but as his prized possession. His guard, Snake, knows his true nature and serves as a quiet foil to his pretensions, while his aged father, Sverkel, remains a silent, immovable witness to his son’s failures.

Ketil undergoes a dramatic and destructive development when faced with overwhelming adversity. The combination of his sons murdering King Canute's men, the king's plot to ruin him, and Arnheid's attempted escape causes his pleasant facade to shatter completely. He brutally beats the pregnant Arnheid nearly to death, losing his own unborn child in the process. Blinded by rage and despair, he abandons his cowardice for a reckless, suicidal charge against Canute's professional army, leading his untrained farmers and retainers to a slaughter. After being defeated and knocked unconscious, he awakens a broken man, devastated by the loss of Arnheid, his wealth, and his false honor.

As for notable abilities, Ketil possesses no significant combat skills or strategic acumen, despite his intimidating physique and false legend. His only real ability is in farm management and the maintenance of his deceptive public image. When he finally leads his men into battle, he is quickly and easily incapacitated, confirming that he was never the warrior he pretended to be.