Jaan is one of the main characters of Dark Moon: The Blood Altar. He is a vampire attending the prestigious Decelis Academy, where he is in the twelfth grade, and he serves as the enforcer for the school's Nightball Team, a position that utilizes his considerable physical power. Within his close-knit group of seven vampire brothers, Jaan is known for his formidable presence and his role as an action-taker, often being the first to act in a situation.

Jaan's personality is defined by a strong, dependable, and unshakeable nature, often described as being as solid as a rock. In contrast to his brothers, he tends to be more closed off and blunt in his communication. This reserved exterior might make him appear distant at first, but it belies a deep, heartfelt care for his fellow vampires. He is fundamentally thoughtful and considerate, with his caring nature residing deep beneath his stoic surface. His motivations are largely driven by a protective instinct toward his brothers, and he is fully committed to their collective safety and well-being. This sense of loyalty also extends to the main protagonist, Sooha, a new student at the academy. Along with his brothers, Jaan feels an inexplicable and powerful draw to her, which becomes a central element of the story's unfolding events.

In the narrative, Jaan is a core member of the seven vampires who find their centuries-long existence intertwined with Sooha's arrival. The group is drawn into a renewed conflict with a rival faction of werewolves, a supernatural race with whom they share a long-standing and bloody history. Within the group dynamic, Jaan's role is that of a steadfast and powerful ally. His primary relationship is with his six vampire brothers: Heli, Jino, Shion, Solon, Jakah, and Noa. The bond between them is the cornerstone of his character, and he demonstrates his loyalty through his actions and unwavering support. While he may be less expressive than some of the others, his commitment to protecting the group is paramount. His connection to Sooha is also key, as her presence triggers memories and feelings that are central to the overarching mystery of their past.

Jaan possesses the standard abilities of a vampire, but his signature power is his immense superhuman strength, which far exceeds that of a normal vampire or human. This physical prowess makes him the group's primary enforcer and a formidable combatant, especially in situations that require direct, overpowering force. As the story progresses, the history of Jaan and his brothers is slowly revealed, including the circumstances of their past lives and their connection to Sooha. While his core personality remains one of a blunt but deeply loyal protector, his development is seen through the deepening of his bonds and his increasing willingness to act not just with force, but with the thoughtful consideration that his brothers know he possesses. Information about specific changes to his character over the course of the series is not available in the provided search results.