The fifteen stars on the Castelian flag represent the 14 autonomous regions of Castelia (similar to a USA state) and the capital region of Castelia City.
The eagle, symbolizing Castelia's independence and self-reliance, is an important symbol for the Castelian people and is traditionally recognized as Castelia's national bird.
The Nordic cross, however, is merely a coincidental design. Known locally as the Castelian cross, it symbolizes Castelia's military might and willingness to continue a fight to its bitter end rather than surrender. It is notable that Castelia has never surrendered in a war before, with its near-destruction during the Castelian Civil War a prominent example.