Looking for a fic
I think it was on Ao3, but could be cross-posted on other sites. First chapter had Percy settling in to Camp Half-Blood, before he was visited and manipulated by Silena. They began the quest in the same way as canon, except that Silena was with Percy, Annabeth, and Grover. I don't remember much more than that.
It could be a self-insert, not sure though.