With Teor dead, Travis is going to have to bring out a new character. Here's some thoughts on what background/connections this new character could have that would ease their entry into the secret club thing going on with the rest of the PCs:
Druid of the Old Path: Druids are here to help the people and fix the world. We haven't met a druid that wouldn't be onboard for finding and reconnecting the lost afterlives. Fighting the Sundered Houses is a little more iffy. And between Thaisha and the general respect for druids, easy enough to slot a new one in. Travis could go with a Circle that's already been introduced, or come up with a new one.
Member of the Cloak: The ritual Thjazi was working on has just been pulled off even though he's dead, so the Cloak should be interested in seeing who did it, and recruiting/allying with them for more. Or Mara could straight up hook them up with a junior member (to make sure Travis doesn't have all the info) to keep everyone in touch.
Fey/Vassal of Royce: A new anchor to Faerie has been made, drawing attention to those who made it. Thimble and/or Julien make a good point of connection/introduction. And such a character is at least locked into opposing the Halovar/Candescent Creed, since they're preaching essentially fey genocide, and the Tachonis for destroying the Golden Orchard. Could even be that Maya Davinos or Lady Aranessa sent them as backup.
Vassal of Timmony: The Schemers got King Gus as an ally for their Magpies. It's possible for him to send a knight or spy or even a Hound (big fan of the idea of a PC Hound of the King) to help the group and stay in contact. And between the Schemers and Soldiers, Timmony is fairly trusted (and a Hound of King especially so).
Falconer Veteran: I can still hear the Falcon's cry. The fight goes on and there's 350 soldiers in Dol-Makjar/the Magpies to pull from. Could be a Torn Banner member for that connection to Kattigan, Thimble, and Azune. Could be a different company and those three (and maybe Bolaire and/or Julien) have encountered this character before.
Member of the Barrowguard: One (part of a) big problem created by the Shapers' deaths has been fixed. Given the Barrowguard exists to keep a handle on the Barrowdells and is about to come under fire for control by the Sundered Houses, a member could have interest in joining up to help. Julien and possibly a recommendation from Alogar could help ease them in.
Those are the big backgrounds to go with and the easiest entry, I think.
Penteveral Student/Staff: Murray's not going to be eager about a student joining the danger. Not sure how she gets on with any other staff besides Dean Kora. But more wizards.
Member of the Totality: Cleric in a godless world. Plus a library pass to ancient texts. But the Hargood base is far away and the groups only have the Seekers' experience with Doctor Talter and Bolaire has a few contacts there to engender trust to such a stranger.
Member of the Revolutionary Guard: One of Azune's co-workers. Could be helpful to have another hidden cop. Inversely, they are someone who could sell Azune out big time, so trust is careful.
Ex-Crow Keeper: Thimble might vouch for them if she knows them. But they might be pissed at the larger group since so many were part of the events that disbanded the Crow Keepers.
Member or Vassal/Worker of the Sundered Houses: Difficult to trust without someone in the party really knowing and liking them, or them clearly being in the shit with their House and looking for other options.
Member of Hal's Troupe: Easier to trust with secrets/the mission for just pulling off the ritual play. But harder to trust for any kind of battle readiness for the battles ahead.
Warlock of Tsul'rekshi: I think she'd be interested in supporting the destruction the party has going on. And at least Tyranny and Bolaire would probably be on board to have that contact. The rest may hesitate more about getting more demon shit involved.
And if Travis wants to be wild:
A Panto Mask: Bolaire will insist on keeping them, fuck what anyone else says. He needs backup against Termina. And it's his sibling. Could be interesting to see that strange sibling dynamic in play, but does require Travis to heed Taliesin's made lore to a certain degree to do it.