Benthos
Proud Mer
Is Barbas the only one who will stick around until the mission is complete regardless if you have partners? I've been going through countless of missions and side missions that he's not involved with and he'll continue to go until I find it suiting to go to the cave in which the Rueful Axe is hidden. I don't like being physically pushed around, sometimes it even throws me off when trying to shoot at a mammoth, dragon, etc. Sometimes it pushes me into traps but that's the rarest. Anyway, are there other characters who will help at an unlimited amount of time until you complete their quest or is he the only one? If he is, then I strongly recommend bringing him along if you need extra help since he can't be killed except by the player.