Nothing is known about Callin's early life. An outdoor hermit, Callin developed his stealth while remaining hidden within the dredges of the woods. Callin stayed as still as death itself and waited calmly until he pounced on any small birds in his path. Callin then proceeded to feast on their carcasses with such thrill at his achievements. For their own reasons, the Order noticed his skills, his approach, and his demeanor and thus Callin was inducted into the Zealots.
In his rounds, Callin patrolled the area along the roads throughout northern Eurviscire. It was during one such patrol that he was located and then fatally beaten by the Viking Eivor, who was allied with the Hidden Ones.
- Like other Zealots, Callin had unique fighting methods and gadgets in his weaponry. Upon Eivor's instigation, Callin wielded a poison-laced greatsword, utilized poisonous grenades and his quick agility, and attacked with poisonous arrows.
- Callin also had an immunity to any poison-related attacks, including his own.
- Like fellow Zealot Redwalda, Callin regretted his part in the Order later in his life.