In my current playthrough I went through the underdark first (from the trader/smuggler cave entrance) but didn't go up in the lift from Grymforge, (portal returned to the Grove area) then did the mountain pass and entered the shadow lands from the hill above the creche (my preferred route to get the lantern more easily).
Halsin was with my camp but not in my party before I went into the underdark (which was his apparently preffered route?) But I camped in there a couple of times and he wasn't there. When I came out of the underdark I went back to the Grove area to camp and he was there, I had the opportunity to tell him I'd found Grymforge etc. When I did the mountain pass part he vanished again.
At Last Light he simply didn't appear until we'd had 2 long rests, which was annoying cos I was waiting to do the Art quest so that I could start moving around the landscape without possibly borking something up.
I got a message he'd left my party but I am not sure when that landed as I wasn't looking (but I noticed it when he didn't show up at Last Light)
I have no idea what the game decision was that made him leave and then reappear later as Thaniel wasn't a thing at the time.
Last edited by Bethra; 12/09/23 08:07 PM.