When Cleo was eighteen, her husband died as every Spartan wanted to - in battle. Alexander himself came to his sister's door to give her the news, and the teenaged mother was suddenly left to worry where she and her children would live. Under Greek law, Cleo inherited nothing. Her brother-in-law absorbed the estate and all of it's holdings, but Cleo and her two young sons were allowed to continue to live on a small corner of the property. She became a comodity again - something for her brother-in-law to sell off to the highest bidder as her legal guardian - and within a couple of years he had found her a new husband. Cleo married for a second time at twenty, and it was this same year that her brother was embraced.

Alexander came to her one night after having disappeared for many months, needing to explain his disappearance to his young sister ... and with that what he was and how he came to be. Cleo asked her brother to give her the same gift, but as a Therion he couldn't. Cleo begged - she was sick of life, sick of the hardship, sick of her new husband, of the politics, of never being allowed to visit her children - but Alexander stood firm.

The two parted ways an hour before sunrise, Alexander apologising one last time to his sister that he could not help her, and walked off into the pre-dawn gloom.

At sunset the next night, Cleo quietly left her husband's house and followed the path she had watched her brother take the night before. She didn't know what she was doing, simply that she was determined to receive the gift Alexander had ... she was determined to escape. She followed the road for two days straight, walking at night in the hopes of finding one like Alexander.

On the third night, she stopped to pray to Persephone - the Queen of the Underworld - and as she prayed for help from the goddess, a figure crept out of the woods and grabbed her. Cleo saw the flash of fangs and raised her voice before she lost her nerve, offering the vampire her husband's household for it's gift of immortality. The vampire was stunned, but Cleo stood her ground and repeated her offer. The vampire agreed and embraced the young Spartan before heading back the way Cleo had come with directions to her husband's home.

Cleo has no clan, but she is still Alexander's sister and she had followed him and Clan Therion throughout history. She is his advisor in all matters, and whenever Alexander makes a move, she is always standing in the shadows to witness his victory. Cleo does not trust any of the new clans coming into the city, especially the Di Nerezza and she highly disapproves of his attraction to Domina, seeing the mad vampiress as a threat to her brother's safety. She keeps her thoughts to herself as much as she can bare though, knowing that every time she does bring up Domina Di Nerezza with Alexander, the conversation always ends in a fight.