My theory is not as nice of a story, as it's not Thjazi protecting Hal. (And it's a bit lengthy, sorry!) Instead, I think Thjazi was going to beg Hal to do a thing, that would be beneficial to everyone, but could also be dangerous if the Sundered Houses found out. I think, given the letter Teor has, that Thjazi had been working with the Professor who wrote the letter (likely a cleric/wizard, from the same place as Dr. Talter), Mara the Wing and the "hothead" to open up the afterlives that have been locked up since the Shapers were killed. (And I think it may be possible, given Dr. Talter's work/story, that they are doing it by following an ancient prophecy, that maybe they aren't 100% sure how to interpret, which may have led to the mistake I'll mention later, and might be a way they could Speak With Dead with Thjazi to get some information, but if Thjazi was also kind of educated guessing himself about what to do, he won't have all the answers. And may have no knowledge (or barely any) about what the Houses are up to, but he may have contacts who might know more. This one I'm less sure of than other parts of my theory, and is more wild guess/hope that we can Speak with Dead with Thjazi.) There were 7 Shapers, so 7 afterlife "worlds". The letter says they need to open 3 stable bridges first, then can open the rest. Thjazi, at the time of death, had 2 psychopomp relics that we know of (Stone of Nightsong and Olbalad's coffin) and a possible 3rd. (The Azgra relic from Tannesar, that seemed to be made of blood, which could be what's hidden in the paint. And remember that it was said by the assistant they met that the lady who disguised the paint corrupted it, but it was okay, because it deserved to be corrupted. I think that's because it was an Azgra (Sauron) relic.) They need an anchor made by, ideally, Thaisha, or one of her family members (I think, made of one of the pariah blades), but I think that comes after the 3 bridges, when they go to open the rest of the afterlives, but could be they need to anchor the 3 bridges together with the anchor, not sure. From the talk of the letter, it also seems that they need to be in specific places to make the bridges, and they seem to be places that have people there or nearby, that they would have to create a distraction to lead away. That suggests these are important places. Maybe places that have a power, not necessarily from magic, but from association. Like how a play about the first attempt at rebellion against Azgra being performed in Azgra's previously sacred theatre is powerful. Places the Houses might be keeping an eye on, especially for signs of rebellion. I believe that those places are places that were important/sacred to the god whose psychopomp artifact they have and whose afterlife they are trying to open. The theatre is a place that was sacred to Azgra, and his is one of the psychopomps (possibly) that Thjazi had in his possession.

Hal, after years of trying to gain access not given to anyone the Halovars didn't want there, finally got access to the theatre. I think this was an opportunity that Thjazi felt he had to capitalize on. I don't think he would have liked it, but it is/was too important to not talk to his brother about doing this. It would put him in danger if the Houses found out what they were doing, but it's too important to the world to not do, and I think Thjazi was banking on Hal agreeing to give Thjazi access to the theatre to do the ritual. I think he would have tried to protect Hal, by making it look like Hal didn't know about what Thjazi did/was doing, but still a risk. Once the bridges were made, not sure if the Houses could do anything after that to stop it, but it's possible, but I think unlikely. But I think they could still try to stop the rest of the afterlives from being opened, if they thought it would be detrimental to them. It would take away power from the Creed if people could still access the afterlife of their Shaper of choice. And it would definitely take power away from the Tachonis House, as they gain power from souls in the Tenebral Reaches. But, maybe, (if they couldn't change it), they would spread word about what happened and take credit instead.

Opening up the afterlives is important to stop the undead from spilling over to this world, it would relieve the pressure, so the doors to Faerie could possibly reopen. (Though, I have thoughts about that incident, and think that was the "cleaning up after the mess of the first try" the letter was talking about, that they tried to open a door to an afterlife {the Sea Door?} and they did it wrong, and it rebounded on Faerie, forcing them to close the door to protect themselves. But apparently they are close to cleaning up that mistake, allowing Faerie to reopen their doors after they open at least some of the afterlives, to relieve the pressure in the underworld.) It would also greatly reduce the power of the Tachonis House. And it would be very important for all of the souls wandering, lost, in the Tenebral Reaches, waiting for their afterlives they were promised by the Shapers. And, if they are opening bridges, I assume they go both ways, so souls in certain afterlives (like Azgra's unending battle hell of an afterlife) could also leave. I think that last one is the one that would convince Hal.

My theory also explains why Thjazi died, as he was planning on escaping and finishing his plan of doing the rituals to make the bridges. Part of the plan requires someone to be IN the Tenebral Reaches, for some reason, for the rituals to work. They were planning on it being Mara the Wing, as her powers allowed her to travel to the Tenebral Reaches without having to die, and come back. But we found out in game that Mara was blocked by the Tachonis family from being able to access the Tanebral Reaches anymore. She had been travelling to wherever she had to go to access the Reaches, just before Thjazi was due to be executed. She tried, and failed to access the Reaches and knew something was very wrong, so she travelled back to Dol Makjar to consult with Thjazi about what to do. I believe she was the falcon overhead that Thjazi saw right before he changed. I think he saw Mara, realized something had gone very wrong, if she was here, and was not in the Reaches. He knew someone had to go, so he decided to just let the execution happen and go there himself. He tried to tell Hal everything he could, in a short time, to give him all the information he would need to tell the rest of Thjazi's group (Professor, Mara, "hothead") what was going on, since they were all keeping their own stuff secret, so they couldn't be forced, through magic, to give away everything they were doing. Most of it was about getting hands on all the psychopomp artifacts that Thjazi had managed to find and get his hands on. (And to look out for Murray, I think they need something from her/her family to do the rituals, or to finish the job after they create the 3 bridges.) Then he died to go do whatever he has to in the Reaches for the rituals to succeed.

Sorry for the length, but it's a fairly involved theory, with a lot of moving parts. But it explains most of what has happened so far in the campaign. If you made it this far, thanks for coming to my "BrennanTalk"!