This is the way I did it:
I went in and out of blosk until I got the message that the shade was there. Then I inched my way up towards where the shade lives. As soon as I was almost in sight (but not yet), I hostiled. I then had my melee fighter get buffed, and head up towards the shade, while the rest of the party sat a safe distance away and waited each turn. My fighter was strong enough that he could survive long enough against the shade to knock off a piece. I then let my fighter got until he died, and had the rest of the pary declare peace after that. Since they were far enough away from the shade it worked perfectly.
Sort of cheap, but it works.