Because sometimes you *want* the walls to be not straight!

I think the reason why the Warcraft III Undead Graveyard's looks so "Halloweeny", is because the tomb doesn't have the regular proportions of a building with straight, perpendicular walls and such, but instead looks very stretched out and distorted.

That way, it looks extra big and threatening, as if it were looming over your head as you approach the entrance, just like a haunted mansion in a cartoon...

It's not very difficult to create this effect in a 3D model, but don't treat the 3D software as a pencil!

Instead of drawing each slanted wall polygon by polygon, create a primitive* and simply stretch the walls inwards (I like to use the scaling tool for this, but everybody has their own preference ;o)

This way, once you break down more complex shapes into separate primitives, you can work fast and create any model you want by combining them! ;o)

Stay tuned!

(*primitives are the most basic of shapes, like spheres, cones, cylinders, cubes...)