Thanatos( god of non- violent death) was ordered by Hades to bring, ( the goddess of the moon) Selene, after she tried killing Hades's creatures and managed to kill several. They fell in love and he never completed his order, so he returned to the Underworld empty- handed.
There she is, Selene, the goddess of the moon.
After Thanatos returned to the Underworld empty- handed, Hades sent The Keres ( female spirts of violent death) to bring their child and to bring them to Hades
The Keres Sisters put 3 spells on Celeste (the child) and she didn't remember anything.
Thanatos declared War but Hades won and he sent him to Tartarus.
All the gods declared war on Hades for kidnapping Selene's child and throwing Thanatos to Tartarus
Hades won and Celeste became the princess pf the Underworld. She started contaminating everyone she passed (the spell of sickness) and her first victim was Omar.