William stayed in the Underworld for two more days because Erinys wanted to stay with her father a little while longer.
To her surprise, Thanatos accompanied her during those two days, and left the workload to his subordinates.
Right now, he wasn't a God of Death, but a father who was doing his best to make up for the lost time that he hadn't spent with his daughter.
Finally, on the second day, Thanatos came to find William, so that the two of them could talk in private.
After making sure that no one could overhear their conversation, Thanatos asked William the question that had been bothering him for a long time.
