To me, the scene with Astarion comes off like he thinks we're a thrall or working with the mind flayers in some
No, he literally says "Hurry! I've got one of those brain things cornered! There, in the grass, you can kill it, can't you? Like you killed the others." And the the knife scene. Why would he try to get our help at killing the brain thing if he thought that we were WITH the brain things? He didn't think that we were under midn flayers' influense. He just tried to kill us because it's what he wanted to do. I can't see how ANY character who is not insane would not kill him right then and there.
