Wait so did Hades know that Persephone was the rightful ruler a long time ago? I understood that when Thanatos finds him drunk in the cave, Hades already knew the truth (I’m only like 30% done with the second book so not sure if this gets answered later on

Well, I’m not going to spoil anything for you, but he knows Persephone is going to be his queen and learns some spoilerific details that make him think she won’t want him.