Maybe. I've heard theories that it's the deities or the City itself. The guides only say so much, you're probably better off asking the people who've lived here.

[She's one of the longer residents, but she isn't about to admit that to Percy. Not when he's clearly grappling with the City as a whole and potentially the news that their dead brother is here with them. Merlin, she wants to ask him if someone's said as much. But then what? Get caught keeping it quiet herself?]

Though probably not until you've let it all sink in. You sound like you're about ready to explode.