Casik and his sister were found aboard the Stravarion Baronsik nearly eighty years after the Great Pilgrimage whereupon it impacted in the Lunaria darklands. While on a mission of mercy to clean up debris which had been scattered about Lunaria for decades, Reverend Rasandiel Gaignun stumbled upon the children who had been surviving on what little technology still functioned within the ship.
The siblings would later go on to play crucial roles in the War for Order, being literal reincarnations possessed of power granted by the foreign gods. Initially, Amistha saw fit merely to use their raw power to fuel the Knights' clandestinely-developed superweapon, the airship Stygian. Eventually, however, forces would conspire to unleash the true power which lay dormant in each.
Casik somewhat resembles Denzel from Final Fantasy VII: Advent Children, having been created as a representation of what the daughter of Zack Fair and Aerith Gainsborough would look like.
Casik is similar to the Russian family name Kozik which could mean either "runaway, goat herder, or ruthless."