In the old BG games, we've met companions along the way, so I'm pretty sure, we haven't been introduced to all potential companions. From the ones in this first area, only Karlach seems to be confirmed? I said in another thread, that I would love to have Alfira and Halsin as companions, love them both.
As for the spider - I think, that would be more of a summon? But I would love to see that. I liked the phase spiders in the Whispering Depths and would love one of them as companion ... even if it would be a bit shrewed, since you basically kill their mother.
I don't think, that Us would be so friendly now to us - every other intellect devourer attacks us now on side, despite them being friendly on the ship. I think, they know by now, that we are not allies anymore - maybe another sign, that the tadpoles in our heads have been tampered with and altered.
I'm ok with keeping the owlbear as a visitor to my camp. It's nice, when he is there, but I somehow have to wish, to keep him out of harms way after all he went through (I didn't kill the mother, she showed me the little one and I left them alone. I did fight and kill her at first, but the scene with the baby was so heartbreaking, that I reloaded).
As for unique companions - I would like to have a Myconid in my group - not temporary as it is the case now (temporary because I don't attack the Myconid colony, like them too much). They are an interesting bunch.
