Have you play the game by yourself? Dark Shiva is block infront of Macalania temple not Farplane's entrance.

And when I return to Farplane in Guadosalam. I do saw Tromell chat to Maester Jyscal but not with Seymour. However, I give a try to call out Seymour and give him a kick all the way to Abyss of the Farplane.