Heres my take, and I think they played with the ordering in the trailer a bit to make people think
That one of Marcone's people died.
Scene 1:
Justine is pregnant. Not really a shocker at this point given what we knew from the sample chapters.
Scene 2:
"The assassin. A creature well known to be your frequent ally." I assume this is Thomas otherwise theres too many plotpoints in this damn book. There are plenty of other assassins or would-be assassins but they tend to not include humans or wizards in the term creature so I feel like once again Thomas is the most likely.
Scene 3:
"What will happen to him?" Evanna responds "Justice". Fairies play word games a lot but the Svartalves are pretty literal and serious in a lot of ways. In this case, I assume she means she believe he will be killed as recompense. I am left to assume Thomas did something to protect Justine since her being pregnant is a big deal to him.
Scene 4:
People who got the invite: Mr Farrow, Evanna, Molly, Marcone, Lara, Carlos/Ebenezar/Chandler/Harry from the White Council are security for the event, and some other dignitaries. At this point it almost looks like Jim was lying to us about the Peace Talks being about the Red Court being gone, though the Fomor might still gatecrash. The trailer could be ommiting the reason for the talks, but they might also be to resolve a dispute between The White Court (Lara is ready to declare war with her new political power and someone took Thomas) and a second party. I think the second party is not Marcone, even though he is Lara's local competition, she is global.
Scene 5:
"This whole conference is Marcone's baby. Hes building alliances." I take it to mean hes operating much the same way he has been for years like with Hades. He is making himself available and playing by the rules so that people get used to seeing him at the table. I assume as Neutral Ground under the accords, Chicago is being declared the place for the Peace Talks. Marcone has been tapped as the organizer and co-host for Mab who called the talks as he is the local expert and Chicago is his territory. He needs the talks to go well, if his power is to grow.... and yet... he is an opportunist. He knows or figured out about Harry and Thomas being related. Even if he didn't, he knows Harry. Harry can't leave a friend to die. And Harry has been a thorn long overdue to be removed. He is setting up a situation where Harry will have to betray Mab to save Thomas, and embarass her at her own peace talks. He is setting Harry up to be removed. That way, no matter what happens, Marcone comes out on top.
Scene 6:
Getting Dressed. "I will pursue my rights under Mab's accords. And She. Will Not. Protect You." He's telling Harry exactly how this will play out if he intervenes to save Thomas. He is taunting him. If you act, as I know you must act, because I know you, then you will be destroyed. She will not protect you.
Scene 7:
"I'm going to take my brother back. And I am going to kill anyone who gets in my way. And you Sir Knight, are going to help me." This is very in-character for Lara. She protects her family with a passion similar to how Marcone protects his people. Perhaps, more so. She needs to if she wishes to remain in power. It's even possible, as we do not know if white females can reproduce, that she needs him to literally keep the house going. She might need him to make baby Raithes with whatever mortal females he can, especially if her father is having trouble. It could also be she sees the baby as a threat, if she can take care of that on her own or get her father to. We don't know. Either way, she intends to use Harry as her weapon like she always has been rewarded for doing. He is after all, the most magnificent weapon she has ever wielded. Not that Harry needs much more motivation, but they have a deal. If either one is about to go nuclear, they have to warn the other one. And they need to keep their shared secret for both of them to remain in power. If anyone finds out about him and Thomas they can end her control just as easily as manipulate harry.
Scene 8:
"Don't think I can't see whats happening." Harry lies lamely. Carlos is seeing some suspicious shit. He knows Harry is supposed to be there for council security but hes conniving with Lara. Hes working for Mab. Hes working against Marcone. Carlos isn't stupid and he knows shit is about to blow up in his face. Security is not going to be going well. He confronts harry about it.
Scene 9:
Harry and Lara in an intimate scene. I find it more likely they are covering up a conversation when they hear someone coming than her having her hooks in him. I am sure winter appreciates the scene though.
Scene 10:
Harry getting ready to fight
Scene 11:
Molly having to save Harry from himself and his bad choices, and also having to protect Winter. You can see the regret in her eyes as she casts a spell.
Scene 12:
"Your choices have made you an outlier" Voice I don't recognize saying your choices have made you an outlier. Now, given, I am used to James Marsters. It could be McCoy but I think the actor sounds different. Possibly Mr. Farrow or someone else.
Scene 13:
Harry in the cage with Thomas, his pants off. Captured?
Scene 14:
Murphy thinking of cutting her cast off. The lighting seems similar to where Maggie is. Could she be watching Maggie for Dresden? Does she need to Gun Up to defend the house, or is she coming to help?
Scene 15:
Harry watching Maggie sleep with Mister
Scene 16:
Ebenezar saying please tell me you aint dumb enough to try this, when he figures out Harry is going to betray Mab and attack the peace talks to save Thomas. This in fact, put him at odds with Harry because McCoy is in charge of security. Harry says he is plenty dumb enough. Queue Codex Alera fury crafting symbols as Harry powers up some spell.
Scene 17:
Harry is in some tight space that is bricked up. It could be undertown, it could be a chimney. Regardless, he is singing a spider man theme song. He is not hiding if hes singing. He could be stuck in a tight space. Trapped? There is some light. Maybe hes deciding if he can lift himself out or get himself out and it will take some strength.
Spoiler Battlegrounds Description:
Harry has faced terrible odds before. He has a long history of fighting enemies above his weight class. The Red Court of vampires. The fallen angels of the Order of the Blackened Denarius. The Outsiders.
But this time it’s different. A being more powerful and dangerous on an order of magnitude beyond what the world has seen in a millennium is coming. And she’s bringing an army. The Last Titan has declared war on the city of Chicago, and has come to subjugate humanity, obliterating any who stand in her way.
Harry’s mission is simple but impossible: Save the city by killing a Titan. And the attempt will change Harry’s life, Chicago, and the mortal world forever.
So... to me I was sure it was Prometheus or Oceanus until I saw her/she. Prometheus was set Free my Hercules.... though it didn't really fit him since he wanted to help humanity.
Oceanus though, was never imprisoned and helped Zeus. He was a big ocean titan and he fathered many river gods and oceanids with his wife Tethys, his sister, who is almost barely mentioned. New thoughts sprung forth. If he wasn't imprisoned in Tartarus, she probably wasn't either... check. What if he is imprisoned now? What if he lies within demonreach? His wife has come to collect him, and she leads the fomor in that endeavor? It says she specifically declared was on Chicago. Harry's town. Not anywhere else.... and the fomor Jim mentioned attack in peace talks... could be her army. Her children.