The leading lady, Scarlet, is a daughter of Gods so she is a ka-jillion-billion years old and has spent that whole time locked up in Tartarus being beat and raped, never knowing any form of freedom.
Her one bright moment was falling in unrequited love with a man, Gideon, who delivered prisoners and suddenly Gideon approaches her, falling in love with her, marrying her in secret and impregnating her with a son. Gideon suddenly disappears and their child is taken from her and murdered in front of her. At the same time she is possessed by the demon nightmares and has to spend most of each day asleep in people's nightmares, forces to participate or she suffers.
Eventually she escapes to Earth for a few hundred years, freedom hindered by her nightmare demon, mourning her son, and searching for her husband. When she finally finds Gideon he rejects knowing her and locks her back up.
She then finds that the Goddess of Memory had messed with her mind and Gideon had never noticed her, much less married her, and her son never existed but the pain doesn't lessen because that had been her reality for in-numerous years.
Scarlet is the most tortured heroine I've read about in a long time and there is no possible ending to give her that would make her's a truly happy ending so I am just sad...