Wow. Don't get me started or I may write something about it. It's perfect!
Time Travel AU (again, I know. get over it) in which the Future Nico looked after his younger self in his homeless days and is the one who sent the dreams to the present Percy Jackson, informing him of what danger the present Nico's in.
I'm loving how I can almost wedge this Time Travel AU into the canon so effortlessly.