Jack is an 11-year-old Saxon boy living in an eighth-century English village. Recognizing his keen perceptiveness and connection to the natural world, the local Druid selects him as an apprentice. He feels unremarkable compared to the stronger village boys but possesses a deep sense of empathy and a quick mind. His training involves observing nature, playing the harp, and learning to interact with the mystical life force.

Thorgil is a young Viking shield maiden traveling with Olaf One-Brow's band of berserkers. She actively seeks glory in battle, driven by a desperate desire to reach Valhalla and prove her worth as a warrior. Harboring a tragic past marked by abuse and abandonment, she uses cruelty to mask her profound isolation and views compassion as a weakness.

The Bard is an elderly Druid from Ireland who resides in an abandoned Roman house near Jack's village. He commands respect from the locals, who bring him food in exchange for his stories and magical protection. Underneath his white beard and impressive cloak, he possesses a dry wit and a profound respect for the life force that connects all living things.

Lucy is Jack's five-year-old sister. With her golden hair and violet eyes, she lives a sheltered life as the favorite child of her father. She firmly believes his tales about her royal origins and relies entirely on her imagination to cope with frightening situations, leaving her dangerously unaware of the real world.

Olaf is an enormous Viking warrior who leads a band of berserkers. Characterized by his massive size and single bushy eyebrow, he lives strictly by his culture's violent code of honor, taking pride in plundering. Despite his fearsome profession, he demonstrates a surprising capacity for domestic gentleness and values the art of poetry.

Queen Frith is a malevolent half-troll who rules the Northmen alongside King Ivar the Boneless. Endowed with supernatural beauty, particularly her flowing red-gold hair, she utilizes her mind-manipulating magic to dominate her husband and terrify his subjects. She is consumed by a relentless desire for vengeance against those who wronged her family in the past.

Giles is Jack and Lucy's father, an impoverished Saxon subsistence farmer. He harbors bitterness over a childhood limb difference that ruined his chances of joining the priesthood. To escape the grueling drudgery of his daily life, he frequently invents elaborate, fanciful tales for his daughter.

Jack's mother manages the household on their Saxon farm. She possesses a quiet, practical wisdom and has minor magical abilities of her own, which she uses to soothe animals and heal small ailments. She strongly advocates for Jack to receive an education rather than spending his whole life doing manual labor.

Ivar is a king of the Northmen who rules alongside Queen Frith. Once a simple bully, his marriage to the half-troll queen has drained his vitality, leaving him deathly pale and exhausted. He retains nominal authority over his warriors but largely defers to his wife's manipulative whims.

Rune is an aging Northman who trained as a bard before a battle wound damaged his throat and ruined his singing voice. He refrains from the crude merrymaking of his fellow warriors, preferring quiet observation. Recognizing Jack's perilous position, he offers his poetic expertise to help the boy survive Olaf's demands.

Bold Heart is a resilient crow missing a claw on his left foot. He exhibits unusual intelligence and bravery for a bird, following Jack out to sea on the Viking ship. The crow quickly proves himself as a clever companion who provides essential comfort when Jack feels entirely alone.

Golden Bristles is an enormous, ferocious wild boar brought across the sea by trolls. Initially aggressive, he responds well to the soothing magical songs Jack learned from his mother. The beast is held captive by the Northmen, intended to be a sacrifice to the goddess Freya.

Heide is one of Olaf's wives, respected and feared by the household because she practices magic. She experiences prophetic visions and quickly senses that Lucy's spirit wanders in strange places. Her protective nature ensures the captive siblings are treated carefully within the household.

Queen Glamdis, known as the Mountain Queen, is the ruler of Jotunheim. Contrary to Saxon stories portraying trolls as foul monsters, she resides in an airy castle and demonstrates profound hospitality. She maintains a deep connection with the environment and mourns her people's displaced history as the world slowly warms.