CarlAia first appeared as a servant to the Dark King, Heros. She introduced herself as a strong vampire with many fighting abilities and that she'd be perfect for his protection. I believe Heros had fallen for her charm more than just hiring her as a guard. I mean, would a man like Heros actually hire a woman to protect him?!
Anywho, CarlAia did come in handy during Hollidai's reign. She was much aid to the Dark Kingdom in taking the young princess down and teaching her some respect.
Seeing as she was a hero to the prince, Mordread, she was turned over to the job of protecting him. Just like his father, Mordread fell for CarlAia's charm and married her. The two were almost invincible as they took over the Dark Kingdom and brought together a whole new gang of members. (Those members will soon have a section all to theirselves. They ain't Dark Kingdom people! :p) These members included: Christian D'Artigan, Midnight, and Ashurei.