He is the first mate aboard the Green Runner, Captain Richard Goldvane's sailing vessel. Stormwalker appears throughout the book, and is most likely going to appear in the prequel installment to ACJ.
His parents are ancient warriors who can control stormclouds with their mystical powers. Though unable to do this himself in ACJ, Stormwalker believes he will some day be able to harness the powers of his parents and further ancestors.
Not much is known about Stormwalker prior to serving aboard the Green Runner. He lived in Austrailia for the first 8 years of his life, before his mystical parents moved back to their ancient temple on a rock island off the cost of France. It is said that the thundering blasts of clouds, winds, lightning and rain never cease at said location. Surrounded by mist, it is incredibly difficult to locate this island. Stormwalker felt so proud to be there, and believed his parents when they told him
"Some day, son... you will control our abilities. You will take the family's strength, power, supernatural control over lightning... and most importantly, you will inherit our everlasting courage."
Stormwalker lived in the temple for 12 years. At the age of 20 he left in search of inheriting his ancestor's control of storms. He wasn't exactly successful, and spent most of his time in bars bragging about his so called "powers."