Solangelo Is Forced Into A Quest Against Their Will

Hecate sends Will and Nico on a quest in the past to protect a young wizard named Harry Potter from Voldemort. They travel back 23 years to 1996 and attend Hogwarts to protect Harry and his friends, until things get a lot more out of hand than expected...
OR
Basically every single Solangelo/Harry Potter crossover fic you've ever read (and I also suck at summaries)