i have a lot of insane twp theories (you don't understand, i've spent like six hours a day for the last three years absorbed in twp), but here's one that I think is actually really plausible.
everyone's speculating on who the twp titles refer to, and here are my guesses:
The Last King of Faerie: Kit Herondale (i mean, he's the only one who has a claim to both courts)
The Last Shadowhunter: Ty Blackthorn (i could do a whole separate post on why i think this is likely, but if you read my last post, you'll understand)
The Last Prince of Hell: Ash Morgenstern
now i know what you're about to say. "claire, that isn't a wild theory at all, it's definitely very likely that lucifer relates to ash in some way."
i don't think lucifer relates to ash.
• cc has said a million times that lucifer will be way different from what we expect. this would DEFINITELY fulfill that.
•if we go back the epilogue of tlbotw, the other eight princes of hell are gathered and they're like "we need to call on lucifer." this makes me think that awhile back, they all realized that lucifer was too powerful and found some way to contain/"kill" him and he "came back" as ash (morgenstern, black angel wings, it lines up)
• if ash is turned to team good (by dru, among other things), then that would turn the whole shadow world on its head. THE prince of hell working with shadowhunters would throw everything into chaos.
• if ash did work with twp gang, with all his crazy intense demonic magic, HE could be the one to permanently close the wards around the world, therefore preventing demons from entering and making it so shadowhunters are no longer needed.
IT MAKES SENSE, YOU HAVE TO ADMIT