Maybe I'm just missing references to some epic Norse saga because I've never been as fond of Norse mythology as I am of classical, but I can't seem to engage in the plot at all. My bad.
I decided to refocus my attention on the PJO-verse of it all, and think about what little things in the latter HoO books and of course The Hidden Oracle might point toward Trials of Apollo clues.
- Reyna was the biggest dropped storyline in HoO. She pretty much got started with a story in Blood, but that was at the very end, and it didn't resolve, so I think she will pretty well have to figure. Given that the last question she was asking was about what Aphrodite said about no half-blood healing her heart, and there was no resolution, I assume that was building up to the Apollo storyline. He is not, after all, a half-blood, and is a healer. Whether that means a romance or not isn't clear. She thinks it is, but that seems like a very odd way to word it. (I'd be cool with it, though.)
- The sword of the pirate Cofresí. Reyna used it to dispatch her father's ghost, but it didn't re-enter the story. Still out there somewhere? One of the oracles is described as being in deep blue water. Sounds Caribbean to me. Puerto Rican adventure on the way? Is there a blue hole around Puerto Rico? Amazons! Reyna! Possible swords?
- Which seems like a more likely heart-wound to be healed. Not getting a chance to make it work with her crush was hardly the biggest problem Reyna had, after all.
- Ella's another dropped point, almost certainly saved to play out here. She memorized the Sibylline books, and the Sibyl of Cumae is one of the Oracles on Apollo's shopping list.
- The bronze fire eater
Was forced death and madness to swallow
Apollo seems to think he's going to be forced to swallow death and madness, but it seems like Festus will, honestly. Dionysus represents madness. Will Dionysus and Hades have something to do with this?
- Also, where are the rest of the gods? In THO, Chiron mentioned that he expected Mr. D to come back after the war, but he never did. Apollo can't remember what happened on Olympus before he was cast out. Iris messages aren't going anywhere. Artemis hasn't attempted to help Apollo (though we saw in The Titan's Curse that he will defy Olympian rules to help her). The only god we saw in THO was the titan Rhea. Which was the book's funniest scene. Is something going on to block them? That would be a good place to bring in Jason, who's supposed to be building their shrines and temples.
- Obviously, Meg has to come back and do something to help destroy the Triumvirate.
- With the big bads being Roman emperors, what's going on at Camp Jupiter? And obviously, the question of which two emperors are the other members is relevant. Diocletian seems like a good bet, since he's already been established (and how to make Reyna and Jason feel disillusioned). Apollo takes pride in Octavian Augustus as a descendant, so maybe...? I don't know my Roman emperors all that well. I should look into it.
- They've started to kind of approach the subject of the Christianization of Rome. I'm not sure that would fit into the mythverse (as from the start, they've separated the gods of Olympus/Asgard/etc from the question of the monotheistic religions' God, and Samirah al-Abbas in the Magnus Chase books explicitly separates the two), but it's a possibility that they'll interact more. (I weirdly loved the scene in Blood where Hades dressed as a monk in Evora.)
- Nico is too much of a fan favorite to be left alone, so I imagine he'll be given a job of some kind. While the ghost-ifying of Bryce Lawrence come back to, well, haunt him? He turned a living person into a ghost. That's a pretty big thing to just be left out there.
- Apollo's relationship with his children is definitely the strongest part of THO. I think he'll most likely end up fighting at Will's side in the final battle. Will's healing skills will play a pivotal role. Maybe keeping him alive long enough to regain his godhood after a sacrifice?
- Now that we have a god as a main character, maybe we'll learn more about the actual mechanics of godhood. Piper thinks once that it's strange for Aphrodite to have so many children the exact same age, but the question isn't revisited. I wonder if we'll learn exactly how much free will the gods do or don't have in these relationships with mortals. Dionysus implied in TLO that their spirits show up whenever they're powerfully summoned, and both Marie Levesque and Beryl Grace are spoken of as having summoned the gods, not being pursued by them. Do they even have a choice at all? Apollo brings it up again as a repeated argument -- in the silly business of how he couldn't avoid wearing a powdered wig in the 1700s -- about how much mortals impose themselves on the gods. It's brought up many times that there are cases where the gods simply are prohibited from acting. Are there also cases where they are made to act? How much of the power actually comes from the mortal parent? Are the children so different from one another because the parents invoked the gods for different reasons? Is there a difference between something like Sally's relationship with Poseidon (where they seem to care about each other like normal exes) and Apollo's little "Oh, yeah, his mom was a folk singer" things? This is just an interesting question to me, and it would certainly change the dynamic of, "Jeez, the Olympians are crap parents" to more like, "Are they even always particularly aware of what they've been invoked for?" Their kids are all ADHD... maybe it's because the gods are literally in so many places at once that they literally have their consciousness split in too many directions to consciously follow all of them.
- American aspect. We saw that the gods picked up a whole new aspect during their time in Rome, so much so that they were their own enemies. Did they pick up British aspects when they were in the British empire? Is the rejoining of the Greek and Roman aspects leading to a new, American aspect?
Guess that's it for now.