1) I think Tessa is a demon with a soul, and Mortmain wants to bind her powers through a magical wedding ceremony. Is it settled that Tessa is a warlock? Magnus says she is, but there still seems to be some doubt. Mortmain clearly wants Tessa for her shape-changing abilities, but how will he gain control of them? If she was a demon, he could bind her to do his bidding.
2) Mortmain will use the Mortal Cup to control Tessa. We know that the Pyxis stores demon energies, and Jem says that Mortmain will need a lot more than is in the Pyxis if he wants to animate his entire clockwork army. How can one summon and control demons, store their consciousness in the Pyxis? If he had the Mortal Cup, which Valentine used in TMI to summon demons, then Mortmain could not only collect their energies for his army but also, maybe, control Tessa. If she was really demonic.
3) Will is going to become a vampire. He already has a predilection for biting, and as a bonus he hates vampires. Thinks they can’t feel or love the way humans can. So, of course, he’s bound to become one. On the plus side, he’ll be an immortal like Tessa. On the down side, he’ll no longer be a Shadowhunter like Jem. I don’t foresee any babies in the future for Will and Tessa, just a long and unhappy life as Downworlders.
I find that anyone who has an extended run-in with a certain group of Downworlders usually joins them in the end. Simon was kidnapped—or, rather,
ratnapped—by vampires in the first book, then became one in the second. Will bit a vampire in CA, had to drink holy water to purge the tainted blood, and argued with Tessa about vampire souls. Obviously this is all leading in one direction: Vampire Will.
Someone on Twitter came up with an interesting theory: Mortmain becomes a vampire in The Infernal Devices, survives the final epic battle in the third book, and lives long enough to become the villain in
City of Fallen Angels. I like that.
4) There’s a demon inside Will, fighting for control of his soul. Epic, I know. If there’s not actually a demon renting a room at the MOTEL WILL, there’s something at least demonic about him. C’mon people, eyes like the night sky in Hell?
5) I have a theory about CoFA and the big betrayal from within. I sent the moderators a post about how I though a demon energy escaped into Will, using him as a vessel of some kind. We know that when demons die, they return to their own dimensions. But...what if their consciousness chooses to escape into another physical form?
Sebastian/Jonathon was born of demon blood, and over the years this blood slowly burned out his humanity. A lot of people have speculated that Sebastian may still be alive in some form, his demon consciousness having returned to a demon dimension once Jace killed him in
City of Glass.
What if he lingered?
There were three people present when Jace killed Sebastian: Jace, Sebastian and Isabelle. Either Sebastian escaped into Jace, or he escaped into Isabelle, laying low and biding his time. The summaries for the next TMI cycle mention that the characters will be betrayed by one of their own. My money is on Isabelle, because she’s someone you wouldn’t expect. But Jace is a good choice too; maybe he’ll lose his soul in
City of Lost Souls and the others will have to reclaim it from Sebastian who takes control of Jace’s body. It might explain his weirdness in the CoFA excerpt.
