"The Brotherhood doesn't always kill on the spot; they take prisoners when they can. They're a very religious bunch who strongly believe in Arceus and put the trespassers through trial, for their God to judge them. That's exactly what happened to the heroes, they were taken (or rather, went there on their will) to the Forest's Heart so they could be tried."
In your case, you can show Elder Durand's letter to get away from the trial and join the others.
Okay, wow, you guys write a lot So I get the general gist of it, I think, so correct me if I'm wrong: the group was teleported to The Forest's Heart, which is Lord Zeke's "lair." They have agreed to work with Lord Zeke and his army(?) to defeat the Cyalan's. They're currently meeting with Grandma Cybella to attempt to get the plate from her, right? How exactly would I bring Loria into that?