By "barrier," Kaelan was referring to Hazerion's bloodline ability, 'Scales of the Overlord.' Unlike the other dragon clans, the royal one didn't inherently possess the exact same dragon crest. Instead, they possessed parts of the full crest that the first proud dragon overlord, the dragon god, had all over his body.
What this meant for them was that each royal family member would possess the crest most compatible with them. However, it wasn't impossible for a royal family member to be born with more than one crest at the same time, as was the case with the second heir, who had three crests on his body.
Although there were also cases where a member born with one crest later awakened another, such instances in dragon history can be counted on one hand.
