Her father is Jack the Ripper.

Artemis has hit her stride as the Blaze. By day her friendship with Liam blossoms, and by night she's the Champion of Light, protecting London from the darkness. Everything's going her way—when a dark stranger from her past appears.

Her biological father, Jack the Ripper, is back, returning through a tear in the Veil between worlds. He claims he's left his evil ways behind, but leopards and murderous psychopaths don't change their spots, and his nefarious plans go far beyond seeing his daughter again. If he gets his way, Hell will literally be unleashed upon the earth.

And you think you have family problems?