There are 2 location for polygon smoothing. One is on the properties panel for the object itself. The other is in the Render options panel. There is a third item that produces this effect: displacement. Given the way the texture details are affected, my guess is it's actually displacement, as the polygon smoothing issue usually doesn't mess with texture that way. However, displacement, with certain meshes (notably square ones involving triangle shaped polygons) can wreak havoc on scenes like this. Ensure that all three are unchecked, and it should work fine -- While I haven't tried all the various DM sets, the ones I have work fine in P5.

thou and I, my friend, can, in the most flunkey world, make, each of us, one non-flunkey, one hero, if we like: that will be two heroes to begin with. (Carlyle)