User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-4902593-20121204103847/@comment-1515612-20121204134901

I think as a writer and you've written about a character's life for so long it's hard to just let him sit there. I think at the same time he also understands that many fans are very young readers and might not be adjusted to the new characters. It's always nice to have something that is familiar.

I'm pretty sure he means The Singer of Apollo.