Necrona is the only living daughter of Draconis.  Draconis had any female heirs killed at birth, but her mother managed to have her spirited away and raised in secret.  She only revealed herself after her father's death and when her brother, Krennick, was framed for murder by his chief adviser.   After Krennick's name is cleared he gives control of their father's realm and his army to her.  She is secretly married to Mercury Blackthorne and has stolen Zephyr Noble's baby (her brother as it is Draconis' child) and is raising it as her own.
 
Necrona is now the sister-in-law of Zephyr as she married Slate Blackthorne.