At attempt #9 I finally got him, and this in spite of Astarte attacking Jahan all of a sudden, the fact that this weak deity is in charge of guarding the god box is extremely disconserting. Obviously knowing that Jahan is a zombie she cast several healing spells to hurt him, fortunately I was able to create a pool of poison for him (next to him, because for some reason he's too dumb to realize that poison heals him) to wade in.
