I tried all conversation options for all 4 characters and he didn't turn up. I had previously freed him by pulling out the spear and then freed his soul by breaking his jar. Perhaps something else is required.
That's odd, it may just be buggy. I've managed to get him to appear on my last 3 runs though (2 last patch, 1 this patch).
All I remember doing is taking out the spear, accepting his offer with my dwarf, destroying his jar without absorbing his soul, going back to loot his body and that's it. Once I get to the barrier, I just need to click on the mechanism to make him appear :
http://imgur.com/JvUlAJZ.jpgConsidering the dialogue options, you may not even need to have found him in Fort Joy for him to appear, since the first option is to wonder who he is. Which, by the way, needs to be changed if we've already met him before.
PS. It seems to have been fixed this patch. You no longer have to click with whoever agreed to help him, my bad. Just tested with my other characters, they also get him to appear by touching the mechanism.
