There is a post running around (probably more than one) about demigods reaching the wrong place. Greeks getting to camp Jupiter, Romans to valhalla and so on.
Now in canon the soul goes to the afterlife the person believed in (I think it was written in one of the TKC books). But canon bows to the will of the fanfic writer, and so many characters died a hero's death the valkyries must have worked overtime.
But who's death was heroic enough? Is Silena, who sacrificed her life to get the Ares cabin to the fight, but died afraid, worthy of valhalla?
Is Beckendorf able to get selected? His weapon was greek fire bombs, which he stuck to a wall. It might not count as "holding a weapon". I legit don't know my books are out of reach and I can't check.
And for full angst, Luke! Is a mental battle for control over his body with the king of the titans and winning for long enough to kill both not an act of heroism? And after some time to come to terms with everything he's done, a blond kinda scrawny teenager called Chase comes and sends him spiralling because his dear sister Annabeth lost another family member.
It can go so many ways! Angst, reuniting fallen friends, Magnus having someone with actual instructing skills teaching him to survive, and so SO much more!
