Caiden is the grandson of Ambrus Valsin, legendary leader of the grand lodge faction of the Pathfinder society, and the man who also runs the day-to-day operations of the Spire.
Ambrus had a daughter, Elsa, from a youthful fling. He was unaware of this child until her son, Caiden, approached him and told him the story.
Cautious at first, Caiden passed all of Ambrus' tests with flying colors. Eventually, after his first year, Ambrus recognized Caiden as his grandson.
For his part, Caiden grew up in a small village Kassen, hearing stories of his famous grandfather from his mother, who worked as a blacksmith in the village. When he came of age, Caiden decided that he was going to join the Pathfinder Society and meet his grandfather. His mother refused to allow this, eventually setting a task before him: if he could plumb the depths of the crypt of the everflame and return unscathed, she would allow it.
Needless to say, he did indeed succeed; in fact, he is credited by the others will keeping them focused and working together to complete the trials.
Once his group emerged from the crypt, Caiden's mother wrote a letter of introduction and explanation to the father she had never known, and sent her son towards what he believed was his destiny.
Three years have now passed, and Caiden is about to take his first step into a wider world than even he could imagine...